HTBA & HVERF
2011 Stud Middle Management Seminar
Basic Reproduction in the Mare Lecture One DR JOHN CHOPIN BVSc PhD FACVSc Registered Specialist in Equine Reproduction, Resident Veterinarian Coolmore Australia
ANATOMY Summary There are 2 ovaries in the mare (right and left). The ovaries play a critical role in reproduction to produce the oocyte (egg) for fertilisation and the hormones that help reproduction. Ovarian size can depend on activity. Small ovaries are found in anoestrus, whereas maximal size and activity is found during the breeding season. Once the follicle has released the oocyte, it collapses and forms the next important structure of the ovary â€“ the corpus luteum. Corpora lutea (the plural of corpus luteum) form after ovulation and can start with a blood clot. The clot then shrinks and is replaced by yellow luteinised tissue which will undergo luteolysis (destruction of the corpus luteum) and form the corpus albicans. During pregnancy extra corpora lutea can form under the influence of endometrial cups between days 40 to 160. The uterine tube joins the ovary to the uterus and is the site of fertilisation and early embryonic life. The uterus is bipartite with 2 horns and a body. The endometrium has conspicuous folds with a cell cycle related to the stage of the oestrous cycle .
Ovary The basic functional unit of the ovary is the follicle. The follicle contains the oocyte (egg) and also the cells that produce the hormones important for sexual behavior and mating. The size of the ovaries depends on follicular activity. The smallest ovaries are found during anoestrus (no sexual activity), dioestrus (when the mare has “cycled off” and is not teasing) and at the end of pregnancy. Once the follicle has released the oocyte, it collapses and forms the next important structure of the ovary – the corpus luteum. The mature corpus luteum is 2 to 3 cm in diameter. A mature corpus luteum is not normally seen with a large number of ovarian follicles. A large number of ovarian follicles are seen with no or a regressing corpus luteum. The largest ovarian follicles are 3 to 7 cm in diameter, however larger follicles can sometimes be present. When the ovarian follicle ovulates to release the oocyte a corpus luteum forms. The corpus luteum starts as a blood clot in about 50% of ovulations (corpus haemorrhagicum). The clot shrinks, and the lining of the crater becomes luteinised (grayish brown in colour). Luteolysis is the process of destroying the corpus luteum. The luteal gland is now called the corpus albicans as it regresses due to its white colour During pregnancy numerous secondary corpora lutea may form beginning on approximately day 40. These are gone after day 160, along with the primary corpus luteum. Not all pregnancies form accessory corpora lutea and there does not appear to be any adverse effect on foetal survival.
Uterine Tube The uterine tube joins the ovary to the uterus. The uterine tube has the amazing capability of transporting male and female gametes, providing the site of fertilisation, and supporting the young conceptus up to day 5.5 to 6 post ovulation, when the embryo emerges from the uterotubal junction into the uterus.
Uterus Uterine type in the mare is bipartite, meaning that it has 2 horns as well as the main body. The surface lining of endometrium is conspicuous with longitudinal folds. The endometrial mucosa has longitudinal folds or mosaic-like folds. The uterus is responsible for receiving semen from mating, sorting good sperm from the semen and ejecting the rubbish, and then supporting the pregnancy from a young embryo to term.
Cervix The cervix is an important structure as it forms a valve from the external world into the uterus. It has to dilate enough to allow semen to enter the uterus (mating) to allow fertilization. The cervix has to stay open long enough to allow inflammatory debris to exit the uterus but close in time to -3-
stop loss of the very small early embryo. The cervix has to stay shut for the entire pregnancy to prevent contamination and infection. The last job is to dilate enough to allow the birth of a foal and then recover without injury.
Vagina The vagina forms the passage from the outside world to the uterus. It has to accommodate the penis of the stallion, allow urine to be dispelled without contaminating the uterus, and form the birth canal.
External Genetalia The external genitalia provide the last of the barriers to contamination and infection to the uterus. They are responsible for sexual display, mating and also the birth of the foal. The external genitalia is delineated by the anus dorsally then the perineum between the anus and dorsal commissure of the vulva. The ventral commissure of the vulva houses the clitoris.
Placenta The placenta is produced by the embryo/foetus and is vital for support of pregnancy. Not only does it allow the transfer of oxygen and other nutrients to the foal, it also is responsible for the removal of waste products including carbon dioxide. The placenta also has to provide a (fluid) environment for the foetus to develop inside, protect it and prepare it for life outside the uterus.
YOLK SAC REMNANT
CHORION AT CERVICAL STAR
PHYSIOLOGY Summary Mares are seasonally polyoestrous, mediated by changing photoperiod, temperature and nutrition. There is a breeding season and an anovulatory season separated by transitional periods. The reproductive physiology of mares is controlled by hormones including melatonin from the pineal gland, GnRH from the hypothalamus, FSH and LH from the pituitary gland, and ovarian hormones including oestradiol, progesterone, inhibin and androstenedione.
Ovulation Prediction Follicles increased in size during oestrus and were tense to touch. In the 24 hours prior to ovulation the follicles felt much softer. Ovulation prediction is difficult. There are several aspects to predicting ovulation. 1. The degree of softness is the most useful criteria for predicting ovulation. The follicle should reach an adequate size along with the definite softening on palpation. This occurs in 40% of mares in the 12 hours before ovulation. The average size of a preovulatory follicle in a Thoroughbred mare 72, 48 and 24 hours before ovulation are 40, 45 and 50 mm respectively. Individual mares are consistent in their range of ovulatory diameters between cycles. 2. The shape of the follicle changes from spherical to pear shaped in 85% of mares in the 24 hours or more consistently in the 12 hours before ovulation. 3. The follicular wall thickens, although this may happen too early to be useful. 4. The fluid in the follicle becomes slightly echogenic using ultrasonography as gra nulosa cells are shed. This may also occur in large degenerate follicles. 5. The follicle stops growing in the 24 hours prior to ovulation. The ovulating follicle was the largest follicle 6 days before ovulation; the second largest had stopped growing during this time. 6. Cervical appearance can also be used to predict ovulation. In maiden mares the preovulatory appearance of the cervix is a deep pink colour with some secretion. The cervix is uniform in shape and flattened due to it being limp with oedema. The cervical opens to 2 fingers in -7-
diameter. In mares that have foaled, the cervix is hard to feel during rectal palpation. It is deep pink in colour with a shiny appearance and is flaccid with oedema. The opening is 4 to 8 cm in diameter.
LUTEOLYSIS The endometrial clock for prostaglandin release is thought to be set when there is a rising level of plasma progesterone following a fresh ovulation. Hence an ovulation during dioestrus is more likely to become a persistent corpus luteum. When prostaglandin is released, luteolysis occurs and progesterone levels drop. This is the signal for FSH release and follicular growth develops.
FEMALE PHYSIOLOGY AND ENDOCRINOLOGY The mare is a seasonal breeder with the peak of breeding in late spring/summer. A transitional period follows when the mare moves from anoestrus to full cyclicity. Shedding of winter hair usually occurs as the mare comes out of anoestrus. Transition is marked by waves of emergent ovarian follicles that usually regress. One follicle eventually emerges and ovulates. This ovulation marks the start of full cyclicity. Oestrous cycles have 2 stages â€“ oestrus and dioestrus. Oestrus is the period of oestrogen dominance; ovarian follicle dominance, maturation and ovulation; and sexual receptivity. Dioestrus is the period of corpora luteal activity; progesterone dominance; and no sexual receptivity.
Pineal Gland The equine pineal gland is a reddish, brown ovoid projection from the epithalamus between the rostral colliculi and thalami at the base of the brain. Its short stalk contains the pineal recess of the third ventricle and a suprapineal recess covers the gland dorsally. The pineal gland is homologous to the third eye in lower vertebrates, and is responsible for interpreting environmental stimuli relating to light-dark cycle and season, with horses being long day-length breeders.
Hypothalamus Contralateral hypothalami face each other across the third ventricle of the brain. They are joined at the base, which continues into the pituitary gland. Gonadotrophin releasing hormone (GnRH), a decapeptide, is produced in the parvicellular neurosecretory cells in the preoptic nuclei. It is produced as part of a larger molecule and separated at secretion. GnRH travels to the anterior -8-
pituitary through the hypothalamic-hypophysial portal system. The hypothalamus releases GnRH to control the pituitary gland release of both follicle stimulating hormone (FSH) and luteinising hormone (LH). During dioestrus GnRH secretion is pulsatile with small pulses interspersed with periodic large pulses. This pattern causes secretion of mainly FSH. GnRH pulses occur every 60-120 minutes in early oestrus and accelerate to every 20-30 minutes as ovulation approaches, leading to a change from FSH to LH dominance. Oestrogen in small amounts and progesterone in large amounts also inhibit the release of GnRH. In the early half of the oestrous cycle, however, oestrogen has a positive feedback control on the release of GnRH.
Pituitary Gland Most of the pituitary gland lies in the hypophysial fossa of the basisphenoid bone below the brain. There are 2 parts to the pituitary gland – the neurohypophysis and the adenohypophysis. The neurohypophysis releases oxytocin into the blood stream. The oxytocin originates from the hypothalamus, in the magnocellular cells of the paraventricular nuclei, which project down into the neurohypophysis of the pituitary gland. The bulk of the adenohypophysis is the pars distalis, which produces reproductive hormones such as prolactin, FSH and LH. FSH and LH are glycoprotein hormones. Glycoprotein hormones consist of 2 dissimilar subunits, called and . The subunit is species specific and identical between glycoprotein hormones. The subunit gives each glycoprotein its biological activity. The anterior pituitary gland produces FSH in response to GnRH release. FSH then travels in the blood to the target organ, the gonads. In the female FSH stimulates ovarian follicular growth. FSH is released in a bimodal pattern with peaks in early and late dioestrus. There are 2 major waves of follicular growth coincident with the 2 surges of FSH. FSH starts to rise 4 to 5 days before an ovarian follicular wave. The peak of FSH is 3 days before the emergence of the wave, which then plateaus for 5 days. The release of FSH is driven by GnRH. Divergence of the dominant ovarian follicle coincides with the decline in FSH 2 days following wave emergence. Oestrogen and inhibin produced from the ovarian follicles act as negative feedback to FSH secretion, while activin increases FSH secretion. LH has a similar structure and chemistry to FSH. GnRH release from the hypothalamus stimulates LH release from the pituitary gland, although there is an association between releases of oxytocin -9-
in oestrous mares and LH release so that repeated sexual stimulation might also increase LH and advance ovulation. LH concentrations are low during the midluteal phase, but rise a few days before oestrus after progesterone decreases due to luteolysis. LH peaks during oestrus at ovulation, and returns to midluteal levels over a few days. LH is thought to be the gonadotroph responsible for luteal support. Ovulation can occur in some mares with a low LH level, indicating that ovulation will occur without a detectable LH surge. The inverse relationship with prog esterone suggests a negative feedback by progesterone.
Ovary The ovaries are the female gonads that are responsible for production of steroid hormones and the oocyte and provide the endocrinological environment necessary to support the early stages of pregnancy. The ovaries of the mare hang from the roof of the abdominal cavity at the level of the fourth or fifth lumbar vertebrae. The left ovary is caudal to the right, but there is a lot of movement and variation in position. The equine ovary has an external collagenous zone around a central parenchyma containing follicles and corpora lutea. The parenchyma surfaces at the ovulation fossa, where oocytes are released at ovulation. The ovary is most active in summer during the physiological breeding season and least active in winter depending on latitude. During winter anoestrus no ovarian activity is present due to inhibition of GnRH by melatonin. Late winter and early spring is the period of anovulatory receptivity called transition. Follicles produce oestrogen for prolonged periods and follicles undergo atresia rather than ovulate. In the normal oestrous cycle, there are two major waves of follicular growth coinciding with the two FSH surges. One follicle is selected to mature, while the other follicles undergo atresia. The dominant follicle ovulates and forms initially a corpus haemorrhagicum (CH) which becomes the corpus luteum (CL) under the influence of LH. The corpus luteum is derived from granulosa cells and is compelled to produce progesterone because it is incapable of converting progesterone to other hormones. Granulosa cells in the ovarian follicle luteinise before ovulation.
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Diagram representing the hormonal interplay of the female physiology.
Diagram representing the oestrous cycle of the mare with hormones in the graph and diagrams of the ovarian structures on the bottom. The red band represents behavioural oestrus.
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Seasonal Effects on Endocrinology Mares are seasonally polyoestrous. This is in response to changing photoperiod, temperature and nutrition. There is a breeding season and an anovulatory season separated by transitional periods. Many mares will remain sexually receptive although the ovaries are in quiescence. Some mares continue to cycle during winter: 16 to 63%. Season can affect the length of the oestrous cycle, through an alteration in the length of the follicular phase. Oestrus was longest in late autumn to early spring and consistently short during late spring and summer. There was a difference in the length of oestrus during summer and autumn compared with winter (6.6 days and 6.6 days vs. 9.3 days), but no difference in the length of dioestrus. In spring ovulation took longer (14 days) compared with summer (10.4 days) and autumn (10.2 days). In spring LH levels were lower and ovarian follicular growth was delayed. Seasonal effects are controlled by the pineal gland. The use of lights and temperature in controlled chambers designed to simulate spring and summer during autumn and winter, hastened the onset of seasonal activity. Other signals are probably involved in the seasonal effect of cyclicity in mares. Thyroxine levels were significantly higher in the cycling mares compared with mares in anoestrus during winter but no causal relationship has been established. Mares in very poor body condition entered acyclicity early, whereas most mares in very good body condition continued cycling during winter. Plasma leptin, insulin-like growth factor and prolactin were greater in mares with good body condition scores. Seasonal effects were mediated through changing levels of GnRH secretion. One study found that total hypothalamic GnRH content was not affected by season. However, the distribution within the hypothalamus was significantly affected by season. Immunoreactive GnRH is present throughout all of the hypothalamus, with the highest concentrations in the most ventral, rostral and medial areas. In summer GnRH accumulated in the most rostral and ventral areas of the hypothalamus. Another study examining the preoptic-suprachiasmatic area, the body of the hypothalamus and the stalk median eminence found that season affected the GnRH content of the hypothalamus, but not the concentration or total number of GnRH receptors on the anterior pituitary.
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Increased photoperiod hastened the response to exogenous GnRH as measured by LH levels. The use of a dopamine antagonist, perphenazine, advanced the first ovulation after spring transition. This may have been through the action of the pituitary hormone, prolactin. LH is low in winter and high in summer with no seasonal pattern to FSH fluctuations. FSH and/or LH concentrations and pulse frequency increased during spring and summer compared with winter and LH decreased in autumn. The decrease in FSH lags behind LH going into winter, so follicles can continue to develop. Season did affect the content of LH in the anterior pituitary, but not the FSH content. LH content of the anterior pituitary increased from the anoestrous to the oestrous period and LH release in response to exogenous GnRH followed a similar pattern.
Transition The breeding season is broken into 4 parts: seasonal breeding season, autumn transition, seasonal anoestrous, vernal or spring transition. The breeding season is the period of polyoestrous fertility associated with late spring and summer. Anoestrus is the period of s exual inactivity and sexual indifference during the winter months. The 2 transition periods are the periods of adaption between summer and winter. The proposed series of inter-related steps involved in vernal transition are: 1. Increasing photoperiod acts on the pineal gland to decrease the secretion of melatonin, and this increases GnRH secretion. 2. GnRH secretion stimulates FSH release, but not LH, because of their respective pituitary gland stores. 3. Ovarian follicular development begins in response to FSH, but follicles are not steroidogenically competent, so low levels of oestrogen are secreted. 4. With time a steroidogenically competent ovarian follicle develops and high levels of oestrogen are secreted. 5. In response to oestrogen, pituitary LH synthesis and secretion occurs. The first ovulation of the year takes place.
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Ovulation Ovulation occurs through the ovulatory fossa and 23 of 25 observed ovulations occurred during the night. Ovulation requires tissue remodeling to release the oocyte. Remodelling occ urs through the action of matrix metalloproteinases such as colleganases, gelatinases and proteoglycans. The intrafollicular rise in progesterone plays an important role in the activation of these enzymes. Ovulation occurs within 48 hours of the end of oes trus, but ovulation can occur anytime (even dioestrus) and the length of oestrus varies from 3 to 40 days.
Ovulation Prediction All the information gathered including teasing, examination of the cervix, rectal palpation and ultrasonography, aims to increase the efficiency of the stud farm by trying to minimise the number of services or inseminations per mare per oestrous cycle. This ensures that the stallion or semen is not wasted in a mare that is unlikely to ovulate within a reasonable time after insemination. This increases the efficiency of stallion usage and maximises the number of mares that the stallion can breed or inseminate in a season. The end point of the examination is a prediction of when the mare is most likely to ovulate.
Teasing The use of a trained teaser to determine which mares are in oestrus will limit the number of rectal examinations required. The teasing process is not exact and some flexibility might be required with mares that are unwillingly to show behavioural oestrus. Adequate exposure time for each mare is necessarily to induce oestrous behaviour. This will be facilitated by yard design to allow all maresâ€™ access to the teaser with minimal competition or dominance from mares higher in the pecking order. The teaser needs to be gentle but determined, and â€œshyâ€? mares might need individual attention from the teaser. This will necessitate facilities designed to minimise injury, but allow the teaser close contact with the mare.
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Cervical Examination Rectal palpation of the cervix can help determine the stage of the oestrous cycle. The cervix is small, closed and firm to palpate under the influence of progesterone during dioestrus. During oestrus the cervix is relaxed, open and softer under the influence of oestrogen. The cervix is small, relaxed, but closed during anoestrus. The oedema and relaxation of the cervix increased as the time of ovulation approached. The secretions in the vagina were very stringy and clear at the time of ovulation.
Cervix in early oestrus, still slightly pale but moist and starting to open.
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Rectal Palpation Rectal palpation of the uterus and ovaries help determine the stage of the oestrous cycle. Palpation of the uterus can provide information, as the tone, the diameter and position are influenced by the stage of the oestrous cycle. Ovarian palpation can determine the activity of the ovaries and individual structures such as ovarian follicles and corpora lutea. Ovarian palpation has its pitfalls; however, as a corpus haemorrhagicum can be mistaken for an unovulated follicle.
Rectal Ultrasonography The use of ultrasound technology has greatly increased the accuracy of assessing ovarian and uterine activity. The ultrasonographic characteristics of the follicular wall were examined to identify the optimal breeding day for mares. The roughness of the follicular wall and the characteristics of follicular fluid on ultrasonography were not useful to predict ovulation. The increasing echogenicity of the granulosa layer and the appearance and developme nt of an anechoic layer underneath the granulosa layer indicated impending ovulation. The appearance of the anechoic layer was more prominent early in the season compared with late season ovulations. The appearance of the anechoic layer was also useful to distinguish which ovarian follicle was likely to become the dominant follicle. The changes in uterine oedema as assessed by ultrasonography have
ovulation. A score from 0 to 5 was given for the degree of uterine oedema from mil to maximal. The start of behavioural oestrus was synchronous with an
Post mortem specimen showing technique of rectal ultrasonography
endometrial oedema score of 2. When the administration of an - 17 -
ovulating agent (hCG) was timed with maximal oedema rather than given when the ovarian follicle reached 35mm in diameter, the ovulation occurred within 48 hours in 80-98% of mares. Endometrial oedema decreases before ovulation, to an average score of 1.3 at ovulation. The most dynamic change in uterine oedema is in the uterine body and this should be used instead of the uterine horns to assess impending ovulation. Persistent anovulatory follicles occurred in about 8% of oestrous cycles. These persistent anovulatory follicles decrease reproductive efficiency since affected mares do not ovulate and fertilization and pregnancy do not occur. Ovulation failure prolongs the interovulatory period and treatment options are limited, as the anovulatory follicles do not respond to ovulating agents. See section following for further discussion.
. Ultrasonograph of a medium sized ovarian follicle.
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THICK WALL OF FOLLICLE
Ultrasonograph of a mature follicle with slight shape change and slightly thickened wall.
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FOLLICLE SHAPE CHANGING
Ultrasonograph of mature follicle with early shape change.
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LUTEINISING THICK WALL
REDUCED FOLLICULAR FLUID
Ultasonograph of 2 follicle in the stage of ovulating with ovarian fluid disappearin g and very thickened follicular wall.
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Ultrasonograph of previous ovulating follicles that have now formed 2 corpus luteums with central blood clots.
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Combination of management tools to predict ovulation No reliable ultrasonographical predictor of ovulation could be found by. In general the combination of softening of a large follicle, particularly when painful on palpation per rectum, and a substantial change in follicular shape can be used to predict ovulation within a 24 hour period. Ovulation prediction is difficult but there are several criteria available to help predict the timing of ovulation. 1. The dominant follicle increases in size during oestrus and becomes tense to touch. In the 24 hours prior to ovulation the follicle feels much softer. The degree of softening is the most useful criteria for predicting ovulation. The follicle should reach an adequate size ( ď‚ł 35mm) and a definite softening should be palpated. Softening of the follicle occurs in 40% of mares in the 12 hours before ovulation. The sizes of a preovulatory follicle in a Thoroughbred mare 72, 48 and 24 hours before ovulation are 40, 45 and 50 mm respectively. There is little variation in the range of ovulatory follicle diameter between cycles in an individual mare. The ovulating follicle is the largest follicle 6 days before ovulation in 82% of mares, and by this time the second largest follicle stops growing. The follicle stops enlarging in the 24 hours prior to ovulation. Forty one minutes prior to ovulation a break or protrusion of the follicle wall at the ovulation fossa is a consistent feature. Thirty minutes prior to ovulation the follicle diameter decreases by 13%. The collapse and extrusion of follicle contents (or ovulation) occurs in about 42 seconds. 2. Follicle shape may also indicate impending ovulation. The shape of the follicle changes from spherical to pear shaped in 85% of mares in the 24 hours before ovulation. The mareâ€™s ovary is unusual in that there is a collagenous zone around the ovary with the germinal parenchyma in the centre of the ovary. This limits ovulation and release of the oocyte through an ovulation fossa on the ventral border. The change in shape of the ovarian follicle prior to ovulation is the follicle forming a channel to the ovulation fossa. 3. The follicular wall thickens prior to ovulation. This may occur too early in the process to be used as an indicator for the timing of ovulation. 4. The echogenicity of the follicular wall increases (100% of mares) and echogenic spots appear within the follicle prior to ovulation (54% of mares). The fluid in the follicle becomes slightly echogenic as granulosa cells are shed. This may also occur in large - 23 -
degenerate follicles. These changes are not consistent enough or close enough to ovulation to be useful in predicting the timing of ovulation. 5. The appearance of the cervix using a speculum can be used to predict ovulation. This method is less accurate for predicting ovulation than ovarian palpation, as the cervix changes in relation to circulating steroid levels, and not in relation to ovulation. In maiden mares, the preovulatory cervix is a deep pink colour with some mucous secretion present. The cervix is uniform in shape and flattened as it is limp with oedema. The cervix is dilated enough to insert 2 fingers (3 - 4cm). In mares that have foaled, the preovulatory cervix is difficult to feel by rectal palpation. It is deep pink in colour, has a shiny mucous appearance and is flaccid and oedematous. The external os is 4 to 8 cm in diameter.
PERSISTENT ANOVULATORY FOLLICLE (PAF) Summary Failure of ovarian follicles to ovulate can occur in spring or autumn transition but also during the season. The follicles appear large and can appear filled with blood. Anovulatory follicles can luteinise but generally fail to ovulate and are infertile. The incidence can vary from 4.5 to 8% but is more common in the late ovulatory season but is associated with age, the use of luteolytic agents and some individual mares. There are a few endocrinological studies that indicate an endocrinological defect as a possible aetiology. Ovulation failure has been seen as a normal event during spring and autumn transition. These follicles might contain blood and fibrous bands. Thickening of the follicular wall is thought to be associated with luteinisation and the administration of prostaglandin can induce luteolysis . The majority of anovulatory follicles last 1-4 weeks, appear resistant to ovulating drugs and pregnancy is unlikely if ovulation does occur. Pregnancy rate for 71 PAF cycles inseminated was 0%. The latest paper on the incidence and appearance suggested some risk factors but did exclude large persistent anovulatory follicles that did not appear to have luteinised.
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Incidence The incidence of PAFs varies from 4.5% (8 of 182 oestrous cycles) to 8.2% (151 of 1694 oestrous cycles). The incidence of PAFs might be lower in the early ovulatory season (5%) and higher in the late ovulatory season (20%) but are likely to occur early or late rather than in the middl e of the season. There was a significant association with age (4.4% incidence with mares 6-10 yrs, 13.1% incidence with mares 16-20 yrs). Recurrence of PAF within the same season was high (43.5%) with the likelihood of having consecutive PAFs was 31.5%. In 6 mares that had a history of PAFs in the previous season, the occurrence of PAFs was 54% of all oestrous cycles. Individual mares had a lot higher incidence of PAFs (25%) than other mares (3% and none).
Ultrasonography Normal uterine oedema was seen in 78.3% of PAF cycles. Endometrial score was not different between PAFs and normal follicles for the 3 days before ovulation. The indicators of impending ovulation (decreased turgidity, loss of spherical shape, echoic specks in antrum, serration of granulosum, and an apical area) did not differentiate viable follicles from PAFs up until the day of expected ovulation. PAF become haemorrhagic by apparent entry of blood into the follicle. There was increased blood flow in the PAF follicles 24 hours before expected ovulation but due to overlap this was not a reliable indicator. The increased blood flow of the PAFs was in the apical area where rupture should occur and in an ovulating follicle, there is minimal
blood flow prior to
ovulation. Ultrasonograph of a persistent haemorrhagic follicle.
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Endocrinology In autumn transition, FSH surges in early dioestrus reduce from 2 to 1 surge per cycle before cessation of cyclicity. LH production was also reduced but this was thought to be linked with reduced FSH production. These authors thought that the absence of the FSH surge in early dioestrus lead to sub-optimal follicular development. The plasma levels of progesterone and LH were not different between PAFs and normal follicles. PAFs can also form during dioestrus. There was elevated plasma oestradiol in the PAF group in the late follicular stage, just before the oestradiol peak (2 days before ovulation) but no difference up until expected ovulation. On the day when mares with a mature follicle where administered an ovulating drug, there was significantly lower plasma inhibin and plasma androstenedione in those mares that had non-viable follicles. Plasma progesterone was measured in 42 mares with PAFs and found to be greater than 1ng/ml in 85.7% of mares. The administration of PG reduced plasma progesterone in these mares. There was an association between the use of hCG or GnRH and the luteinisation of the PAF.
Aetiology Individuals appear to be more prone to the condition. It appears to increase with age and more likely to occur early or late in the season. There are endocrinological aberrations that point to this being involved. The failure of FSH priming in early dioestrus, the increased level of plasma oestradiol and low plasma inhibin and low plasma androstrostenedione in the late follicular stage. The use of cloprostenol to short cycle dioestrus might induce some individuals to produce PAFs and it appears to be dose dependent. The premature stimulation of a young follicle with LH/hCG could induce premature luteinisation without follicle rupture as seen in pregna nt mares under constant stimulation with eCG. The use of PG can release LH and this might be the mechanism of the effect of cloprostenol on PAFs.
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From (Ginther, Gastal et al. 2006).
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From (Ginther, Gastal et al. 2006).
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From (Ginther, Gastal et al. 2006).
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PHARMACOLOGICAL MANIPULATION Summary Human Chorionic Gonadotropin (hCG – Chorulon) is used to induce ovulation when there is a mature ovarian follicle (35mm). Ovulation should occur 36 hours post injection (2500 IU, IV), but this depends on the time of the season, the maturity of the ovarian follicle and possibly previous exposure to this large antigenic molecule. Mares early or late in the season tend to act unpredictably with delayed response early or late in season or early ovulation in the late part of the season. One typical protocol is the use of hCG on a mature follicle with mating or insemination planned 24 hours after injection. Gonadotropin releasing hormone (GnRH – Ovuplant) is a pellet injected under the skin designed to induce ovulation when given on a mature ovarian follicle. Ovulation should occur around 44 hours post injection. Response is a little more dependable with mares that may have developed antibodies to hCG and are showing a subsequent delayed response. This drug is more expensive and the main use is for frozen semen insemination, because the ovulation timing is in a smaller, tighter time period than with hCG. This hopefully requires less palpations and therefore less work than with the use of hCG. Cloprostenol (Estrumate) is used to induce luteolysis, however, has a high rate of side effects. This drug has uterine contraction/spasm inducing properties. In cases with excessive uterine oedema, mucoid luminal fluid or were prolonged contraction for 5 hours is desired, cloprostenol might be useful. Altrenogest (Regumate) is most commonly used in nonpregnant mares to help shift from transition to full cyclicity. The use of Regumate should be restricted to mares that some ovarian follicles 25mm in diameter. With smaller or less ovarian activity Regumate is unlikely to work. The mare is kept on Regumate for a period of 10 days and examined. If therapy has worked there will be a large mature follicle or a fresh corpus luteum. The mare should continue to cycle normally. Progesterone Releasing Intravaginal Device (PRID) is seen as a cheaper way of administering progestagen for 10 days. There are some limitations to their use. The first is that the response is not as dependable as Regumate, so ovarian follicles of at least 30mm should be present before a - 30 -
response to therapy is expected. Another limitation is the induction of a vaginitis, which will delay mating or insemination for 2-3 days until the vaginitis resolves post removal of the PRID. Problematic mares, especially with a history of endometritis should not be considered for PRID therapy because of the development of vaginitis. Oxytocin is used as a uterine contractility drug. Doses of 10-20 IU are used, any higher will abolish rhythmic contractions that expel fluid and induce spasm. The effect lasts 1 hour, so a frequency of up to every 2 hours can be used. Although work has been done to confirm oxytocin benefits, none has been done to investigate ideal dosing rates and intervals. Propantheline (Propan B) is used as a parasympatholytic to relax the rectum for rectal palpation. The most common indication we use propantheline for is to induce rectal relaxation for multi ple pregnancy reduction (twin squeeze). The dose is 100mg given IV, the desired effect is within 30-60 seconds with the rectum relaxing, after several minutes the uterus loses tone and is hard to locate by palpation. So the window for the desired effect is immediately after rectal relaxation and before the uterus loses its tonicity. There are 3 stages to consider with pharmacological manipulation of the mare â€“ anoestrous, transition, and cycling mares.
Anoestrus The manipulation of mares in deep winter anoestrus can be useful for breeding mares out of season or assisting mares that are not cycling normally during the breeding season. GnRH has been used to induce follicular activity but a single injection of 1-4mg of GnRH produced no effect. Three to 4 injections of GnRH at 10 day intervals plus concomitant progesterone treatment induced follicular development but failed to produce ovulations. The administration of GnRH in a pulsatile manner induced ovulation in 4 of 4 mares. The use of slow release GnRH caused ovulation in 13 of 18 ponies (76%) and 120 of 136 Thoroughbred mares (88%). Ovulation was induced in a dose dependent manner with an osmotic minipump delivering GnRH. Ovulation was achieved in 7 of 10 mares with 100ng GnRH/kg/hr. GnRH has also been used as a SC depot injection and at the high dose rate (90 ď g/day) the ovulation rate was 58.8% and this took 12.9 days to induce ovulation. A protocol for using GnRH was applied to acyclic mares during the breeding season and 86 of 108
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mares (80%) ovulated. The fertility of these ovulations during the breeding season ranged from 4348%.
Transitional The induction of ovulation in transitional mares is useful with the pressure to breed late in the transitional or early in the ovulatory season. A single injection of GnRH (2-4mg) induced ovulation in 20 of 30 transitional mares, 12 to 96 hours after injection. The use of GnRH analogue busrelin given as a twice daily IM injection induced ovulation in 7 of 15 mares. A subcutaneous implant induced ovulation in 9 of 15 mares whereas none of the controls ovulated. The repeated use of a GnRH implant in late transition could accurately induce ovulation. The use of allyl trenbolone â€“ Regumate is a popular pharmacological method to shift mares through transition. Thirty two of 33 ovulated in response to the use of oral progestagen (30mg allyl trenbolone â€“ Regumate). Clinical experience suggests that mares in late transition are more likely to respond to Regumate than mares in earlier stages of transition.
Cycling Mares are either in oestrus or diestrus during the ovulatory season. Pharmacological manipulations are either aimed at inducing predictable ovulation in oestrus or changing mares from dioestrus to oestrus. Although there is a small need to delay ovulation in oestrus when delayed inseminations are required. The inability to accurately predict ovulation makes timed matings and timed insemination (such as with frozen semen) a labour intensive process. Ovulating agents, such as gonadotropin releasing hormone (GnRH) analogues or human chorionic gonadotrophin, narrow the window of ovulation timing, assist in synchronising and predicting the timing of mating/insemination with respect to ovulation and can hasten ovulation if administered when a mature follicle (ď‚ł 35 mm) is present. These greatly decreases the work needed to monitor mares that require timed mating or insemination.
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Human Chorionic Gonadotrophin (hCG) hCG is a glycoprotein hormone with an and a subunit that is produced by cytotrophoblasts of the chorionic villi of the human placenta. It appears in the urine a few weeks after conception and reaches a peak at approximately 50 days of pregnancy and then decreases. hCG is used to reduce variation in the time from onset of oestrus to ovulation, and reduce the length of oestrus. hCG has a LH like action on ovarian follicles and is administered when there is a large (35 mm in diameter) mature ovarian follicle. Administration of hCG (2500IU) should cause ovulation between 24 to 48 hours after injection. The use of hCG does not adversely affect fertility, and breeding efficiency is improved with less services by the stallion required. There is some suggestion that the use of hCG might improve fertility, as the pregnancy rate per cycle and pregnancy rate per mating was higher in the hCG group (74%, 74%) compared with the control group (40%, 31%). Repeated use has the potential to develop refractoriness or anaphylaxis. Although 100% of treated mares produce anti-hCG antibodies with one to four injections of hCG, the re is not a strong correlation between antibody titre levels and the failure to respond to hCG, or cross-reactivity with LH. It is currently recommended that hCG be not used more than twice a year in the one mare.
Gonadotrophin Releasing Hormone (GnRH) GnRH is a decapeptide produced on ribosomes of the rough endoplasmic reticulum as a prohormone in the hypothalamus. It is then cleaved when it passes through the plasma membrane. Negative feedback to the hypothalamus is from steroid hormones. Protein hormones are not soluble so their receptors are on the outside of the plasma membrane. They modify the secondary messenger system. Peptide hormones are inactivated and degraded by elements in the blood, liver and kidney and then excreted. The administration of GnRH to mares during anoestrus and transition stimulates ovarian follicular development and ovulation by increasing FSH.
Deslorelin Deslorelin (Ovuplant TM, Peptech Animal Health Pty Ltd, NSW) is a synthetic GnRH analogue, which is presented in the form of a biocompatible slow-release pellet, which stimulates the release of LH and FSH from the pituitary gland. Each implant contains 2.1mg deslorelin (as deslorelin acetate). - 33 -
deglycinamide)}GnRH. The product is a biocompatible pellet, which causes no systemic side effects and minimal local reaction. Deslorelin stimulates the release of luteinising hormone (LH) from the anterior pituitary, thus the administration of a deslorelin pellet induces ovulation within 48 hours in 80 â€“ 96% of mares with a mature follicle. The efficacy of deslorelin inducing ovulation is equal to hCG. There is no evidence of refractoriness with repeated use, although recent work suggests there might be an increase in interovulatory period with repeated use of deslorelin in a small number of mares. The interovulatory period was significantly lengthened when control ovulations (22.0 days) were compared to those after the administration of 3 deslorelin implants at once, or one deslorelin implant administered daily for 3 days (36.8 days). Gonadotrophs were lower in the subsequent dioestrus when deslorelin was used to induce ovulation, with FSH and LH suppressed for at least 14 days after deslorelin administration. Despite early work to suggest that deslorelin does not have any negative side effects, the body of new work suggests a hypothalamic and/or a pituitary suppression in most mares for up to 2 weeks post administration.
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Cycle and Hormonal Revision; Cycle Modifications Lecture Two DR ALLAN GUNN BSc.Agric; BVM&S; MACVSc (horse medicine; reproduction); MRCVS; Diplomate ACT
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Cycle Definitions In the mare, it is easier to define the beginning of the cycle as the day of ovulation. The mare is in oestrus for approximately 4-8 days. Shows signs of heat/ in season/horsing. Also known as the follicular phase. The cycle length is approximately 23 days, leaving approximately 17 days of dioestrus. No obvious signs associated with this period. The non follicular, or luteal, phase.
Oestrus 6 days
Dioestrus 17 days (13 days PG Response.)
Oestrus Cycle The oestrous cycle is controlled by hormones. Hormones are produced in various parts of the body. These hormones have effects on various tissues or organs within the body. It is the link between the production of hormones, the inter-related effects of these hormones, and their effects on organs in the body that is known as the oestrus cycle. It is important to realise that it is a cycle, and that the phases move from one to another in a methodical and co-ordinated manner.
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Organs, Hormones and the Links Organs Brain
Surge and Tonic Centres
Vestibulo-vagina and vulva
Hormones This review will be examining and discussing SIX of the main hormones involved in the reproductive cycle of the mare. Gonadotrophin Releasing Hormone GnRH (‘The Driver’) This hormone is produced in the hypothalamus, and is a small peptide (not big enough to be a protein). Effectively this is the ‘Driver’ of the reproductive cycle. It is released in pulses and in minute quantities. It is secreted into a portal blood system, that takes it directly to the pituitary.
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Follicle Stimulating Hormone - FSH (‘The Stimulator’) This hormone is produced in the pituitary and is a glycoprotein that is formed in two subunits, alpha and beta. This hormone ‘recruits’ follicles from the ovary, stimulating them to grow. Luteinising Hormone - LH (‘The Ovulator’) Also produced by the pituitary, a glycoprotein in two subunits. This hormone induces final growth of large follicles, and induces ovulation. Oestrogen - E2 (‘The Receptor’) This hormone is produced by a developing follicle, so produced in the OVARY. It is a steroid hormone, that is relatively big, fat soluble and transported around the blood with carrier proteins. This hormone is important is preparing the reproductive organs, and the brain for copulation. Oestrogen controls signs of Oestrus. Progesterone - P4 (‘The Regulator’) This hormone is produced by the ovulated follicle, or corpus luteum (CL), ie the OVARY. This is also a steroid hormone. This is the hormone that is responsible for the maintenance of pregnancy, and for the outwardly quiet behavioural signs. In the mare, it is mainly the lack of P4 that is responsible for oestrus-like behaviour. This hormone is the ‘Regulator’ of the cycle. Prostaglandin - PGF2alpha (PG) (‘The Terminator’) This hormone is produced by the uterus. It acts on the mature CL. This lyses, or breaks down, the CL so that it stops producing P4. Under the influence of P4 (so a CL is present), the Hypothalamic tonic centre produces low levels of GnRH. This induces release of FSH, which recruits follicles from the ovary. These follicles start to get larger. They produce E2. The uterus does not detect a pregnancy, so there is NO Maternal Recognition of Pregnancy (MRP). The uterus then produces PGF2a. This lyses the CL, so the production of P4 ceases. Now that there is no P4, negative feedback on the surge centre is removed.
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The follicles continue to get bigger under the FSH effect. More E2 is produced by the growing follicle. E2 has a NEGATIVE feedback effect on the FSH, so FSH production begins to decline. E2 has a POSITIVE feedback effect on the SURGE centre, and LH production is increased. This allows the follicle to mature, and to produce more E2. The E2 has effects on the reproductive system and brain. This induces the changes we recognise as Oestrus: Behavioural signs of looking for a male, squatting, urinating, winking and finally standing to be mounted (â€˜breaking downâ€™). Ultrasonographically we see a large follicle, and uterine oedema. Visually, an open cervix, and relaxed vulva. Ultimately, the hypothalamic surge centre produces a surge in GnRH production. This induces a LH surge, and the mature or ripened follicle ruptures. The oocyte, or egg, is released from the ovulation fossa which is unique to equids, and travels down the uterine tube to meet the sperm waiting for it, hopefully uniting to form an embryo. Formation of an early embryo is typically very successful, usually in the region of 90% or more. The embryo enters the uterus after about 5-6 days from ovulation. The ruptured follicle then fills up with blood. Initially this is called a corpus haemorrhgicum (CH). This matures into a CL, which starts producing P4. And the cycle goes around again.
Follicular Dynamics Illustration
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Hormonal Feedback Loops
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Ultrasonographic Detection of Cyclical Changes Per rectum palpation and ultrasonography are the cornerstones of stud farm reproduction. That is not to say that other parts of the management of brood mares is not important, in fact to the contrary. Having as much information as possible, such as history, teasing, age, foal age and mare idiosyncrasies enhances breeding success. That makes it so important for you to be part of the whole breeding system. Effectively the cycle can be followed by palpation and ultrasonographically by scanning the ovaries, uterus and cervix. The cervix and vagina/vestibule can be palpated and scanned per rectum, but are more effectively monitored visually, using a speculum, or direct palpation.
Ultrasound Ultrasound involves the use of very high frequency sound waves that are emitted from, and recorded by a transducer. Fluid looks black, dense tissues such as a CL look white. In between density of tissues are variable shades of grey. Air and bone reflect all the ultrasound waves, and shows up as a white line. It is a very safe diagnostic procedure.
Ovary The normally functional ovary is about 5-15cm in diameter. This varies with follicular sizes. Follicles grow from microscopic size, to about 50 mm in size at ovulation in the early season. Ovulation size tends to decrease as the season progresses. The size of the follicles is detected by ultrasound, typically being noted from about 25mm in diameter. Deviation occurs at approximately 20-25mm. They grow at about 3 mm/day, and ovulate at approximately 40-45mm.
Uterus The uterus is an approximately T-shaped tubular structure. At the back of the uterus is the cervix, which is a muscular and fibrous structure. The uterus consists of the body, which runs towards the head from the cervix, forming the lower part of the T. The uterine horns, of which there are two, branch out to the left and right forming the upper part of the T. Each of those portions of the T are attached to the ovary by the uterine tubes (sometimes called oviducts). - 41 -
As the cycle progresses, and the follicles grow producing more E2, the uterus appears to be more oedematous, ie. has more fluid within the tissues. This is seen on ultrasound as a slightly larger tubular diameter, with increasing visibility of ‘folds’. On the screen this has an obvious ‘cart wheel’, or ‘cut orange’ effect. The oedema and follicular size tend to increase simultaneously.
Cervix This is an important barrier to the uterus, and consists of smooth muscle and fibrous -like tissue. It also contains mucus secreting cells. The cervix undergoes changes during the reproductive cycle reflecting this importance in allowing the entrance of sperm in oestrus, and preventing entrance of contaminants when not in oestrus- dioestrus or pregnancy. During oestrus, the cervix is relaxed, ‘floppy, pink and open. This allows sperm to be ejaculated directly into the uterus. Being open also allows the Uterine Defence Mechanisms to clear the uterus of contaminants after copulation. When in di-oestrus, the cervix is tightly closed, contains varying amounts of mucus, and is white or pale in colour.
Vulva Although not examined ultrasonographically, it is readily examined visually. During oestrus the lips are flaccid and relaxed, similar to that noticed at foaling. When not in oestrus, they are tightly closed and firm.
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Altering the Oestrus Cycle There are two phases of the cycle Luteal Phase Long; CL present; Dominated by Progesterone. Follicular Phase Relatively short; Follicles present; Dominated by Oestrogen. From this, it can be seen that the most effective way of altering the cycle is to alter the length of the luteal phase.
Increasing Luteal Phase Primary Reason:
Done by substituting P4 for longer than ‘normal’. This does not always work effectively in horses, as it does in other species such as ruminants, as mares may ovulate under the influence of P4. So called ‘Dioestrus ovulation’. Method:
Altrenogest (Regumate ®)
Daily P4 injections Intravaginal devices (CIDR®; Prid ®; Cue Mate®) Implants (not licensed for use in horses, eg Crestar®)
Decreasing the Luteal Phase: This is a relatively common practice in theriogenology. It is typically by administration of PGF2a. and is required to be administered once CL is susceptible. Doses used can be as low as 0.1 ml cloprostenol (Estrumate® or similar). Thus susceptibility depends on dose, and age of CL. Usually after 4-5 days. It is important to note that when the mare actually shows signs of oestrus, will depend on the follicular dynamics- presence of follicles that are growing, or grown. Hence the importance of understanding the effects of growing follicles.
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In the thoroughbred industry, if there is a large follicle present at the time of PG administration, it is possible that the mare will ovulate before she will stand to be served by the stallion. Typically about 48 hours is required between PG lysing and CL and a mare standing for service.
Increasing the follicular phase In the mare this is not easy or practical, as the mare may ovulate under the influence of P4.
Decreasing the follicular phase This is commonly done in the TB industry. Using ‘ovulating’ drugs such as hCG (Chorulon®); deslorelin implants (Ovuplant®) or the ‘new’ deslorelin injection. It is important to note that this is not always successful, but has a success rate of approximately 85%. If the follicle ovulates within about 36 hours, it implies the follicle has probably ovulated on its own. The follicle needs to be mature enough to respond, and is typically more than 30mm in diameter. Other GnRH agonists include buserelin (receptal ®), gonadorelin (native GnRH ‘fertagyl®’) and a new one being trialled at present is ‘Historelin’.
Spring, or Vernal, Transition Approximately 80% of non pregnant mares outside of the tropics, will cease cycling in Winter, known as Winter Anoestrus. That means there are two transition periods; one from cycling to not cycling, in autumn. The other from not cycling to cycling, in the Spring time. The initiation of cyclicity is effectively the same for all periods from non cycling to cycling, these are at puberty, in Spring, and after foaling.
It is important to be aware that transition does not happen overnight. It is a long slow process that takes from 45days, usually about 60-90 days to occur. The full stimuli to initiate transition are still not fully understood, nor is it understood why some mares do not stop cycling.
Undoubtedly, this is one of the most frustrating periods to deal with in the thoroughbred industry. Transition starts with an increase in GnRH release from the hypothalamus. This is most likely from the tonic centre. The effects on the hypothalamus are probably integrated by ‘higher’ centres in the brain, and involve a series of complex inputs to the hypothalamus. Recent work has shown - 44 -
that the final pathway is by chemicals known as Kisspeptin, which encourages GnRH release, and RFamide related peptides (RFRP’s) which discourages GnRH release. The tonic release of GnRH encourages the release of gonadotropins - FSH and LH- from the pituitary. FSH appears to present within the pituitary, whereas it appears that a part (Beta subunit) of the LH requires to be made (synthesised) by the pituitary. The release of FSH encourages the growth of follicles within the ovary. These follicles produce oestrogen. The oestrogen feeds back on the tonic centre to produce more GnRH, so more FSH. The oestrogen prepares the mares reproductive organs, and brain for oestrus. However, it is reported to take about 3.7 waves of follicles, at about 14 day intervals to occur before ovulation will occur. (3.7 x 12= 45 days). Once a mature follicle develops, known as steroidogenically competent, LH is manufactured, then released by the pituitary. It appears that it is the concentration of oestrogen that induces the final production of LH. A follicle that produces enough oestrogen, and has enough LH receptors (LHR’s), can now exert positive feedback on the surge centre of the hypothalamus. This GnRH surge induces an LH surge, which induces ovulation. Once ovulation has occurred vernal transition is COMPLETED.
Higher centre input to hypothalamus.(LIGHT)
Increased hypothalamus GnRH
Pituitary FSH release.
Oestrus behaviour- variable.
Steroidogenically competent follicle
LH synthesis and release from GnRH surge
OVULATION and the end of transition
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It is also important to realise, that during this time, the uterus requires to be ‘activated’ by the P4 and E2 produced in transition, as it has also been dormant during the anoestrus period.
‘Higher Centre’ Input There are many parts of the brain that detect body and environmental changes, and produce chemicals and transmitters that ultimately act on the hypothalamus . These include Leptins (nutrition), corticosteroids and adrenaline (stress), opioids and MELATONIN. Melatonin is produced from the pineal gland, which is affected by light detected by the eye. Increased periods of darkness relative to light, induces the production of an enzyme that is involved in the final pathway in the production of melatonin. So increased light means less enzyme, and less melatonin produced. Melatonin in long day breeders, such as the mare, inhibits the release of GnRH from the hypothalamus. So by increasing light- day length- less melatonin is produced, and GnRH secretion is encouraged. That is thought to be one of the main mechanisms for synchronising vernal transition. Prolactin, a short protein, is also produced by the anterior pituitary. This increases with increasing daylight, and its release is decreased by the presence of dopamine. Domperidone blocks the action of dopamine, thereby increasing prolactin.
Management of Vernal Transition Light From the discussion on the initiation of vernal transition, it can be deduced that LIGHT is probably the single most important factor in starting vernal transition. Giving barren mares access to increased day length around the time of the winter solstice (shortest day) is the most reliable method of enhancing vernal transition. There are at least two important points: 1. Vernal transition cannot be shortened with the addition of light. It takes about 60 days (2 months) for transition to occur. The aim of lights is to bring the whole - 46 -
period sooner in the year. So placing mares under lights needs to be started at least by 01 July in the Southern hemisphere breeding of thoroughbreds. Ready for 01 September breeding date. 2. Light needs to be added at the end of the day, and needs to be bright enough so that a newspaper can be read in that light. Making at least 14.5 hours of light in total for the day. The lights should not be left on all night.
Nutrition Mares in good condition, not too thin or too fat, tend to cycle more readily earlier in the season. There have been more than one report of the ‘green grass’ effect encouraging the end of transition. Nutrition is obviously an important part in the reproductive cycle. Other Management Factors: Mares should not be stressed, as corticosteroid, opioid and adrenaline release decrease GnRH release. Temperature has an added effect, if animals are warm and comfortable, they are more likely to cycle sooner. It is interesting to note that light is also the main factor governing coat length, not temperature.
Pharmacological (Drug) Assistance in Vernal Transition There are many drugs used with varying success in manipulating vernal transition. Typically they are not very successful, and that is why there are many and varied treatments. Light is undoubtedly the most important single factor in inducing vernal transition. GnRH or analogues Deslorelin implant (Ovuplant ®); Goserelin implant (Zoladex®); Buserelin injections (Receptal®); Gonadorelin (Fertagyl®- licensed for use in cattle and rabbits only).
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Caution needs to be exercised for a number of reasons:
Implants can also ‘downregulate’ the pituitary (FSH/LH), so may end up prolonging the transition period.
The doses of injectables tends to be relatively high, and often need to be given frequently. This is costly, often with a poor response.
Some of the drugs are not licensed for use in horses, and have no proven efficacy. Dopamine Receptor antagonists Typically in Australia this is Domperidone. Other drugs include sulpiride and metoclopramide. The efficacy of this drug is variable, and it appears that sulpiride may be the most effective in this family of drugs. FSH A synthetic equine FSH (reFSH) has been used in the USA, although it is once again not available. It’s main use has been to try and superovulate mares for ET programmes. It has shown promise in enhancing the vernal transition. Other crude extracts of the pituitary of the horse have been used with minimal success. Porcine FSH (Folltropin ®) has been used with limited success in the mare. LH hCG (Chorulon®) has FSH and LH effects in most species, but mainly LH effects in the mare. The transition period may be shortened slightly by administering hCG to mares with a large steroidogenically competent follicle that is taking time to ovulate. Oestrogen In theory, the use of oestrogen may be possible. Practically it tends to increase the length of transition due to it’s negative feedback on the tonic centre. Prostaglandin Theoretically administration of PG has resulted in an increase of FSH in the brain. Practically it is not used. - 48 -
Progestagens Typically this involves the use of Regumate ®, or use of an intravaginal device such as CIDR®, PRID®, or Cue Mate®. The theory behind the use of progestagens to enhance the progression of vernal transition, is to allow the build up of LH in the pituitary whilst under the influence of the progestagen. This treatment meets with variable success. Mostly, the use of true progesterone, as is found in the intravaginal implants, appears to be more effective in hastening vernal transition than does the synthetic regumate. However, they all appear to be useful in synchronising the end of the transition phase. Importantly, most drug treatments should be considered as an adjunct to management options, especially LIGHT. These drugs are usually more effective as the mare is nearing the end of transition. Transition is one of the most frustrating conditions to deal with as a stud worker, veterinarian, owner, and stallion manager. Kisspeptin The possible use of Kisspeptin to induce ovarian activity in anoestrus may be the next exciting option in the quest to ‘conquer’ vernal transition frustrations.
Foal Heat After foaling, the mare quickly starts to cycle once again. It takes between 8-20 days before the mare will ovulate. It is the same sequence of events that occurs at puberty, and vernal transition, as occurs post foaling. GnRH is produced in response to the decrease in progesterone after foaling. This leads to a pituitary release of FSH. Follicles start to grow, such that they are about 35mm a t approximately 10 days post foaling. They produce oestrogen that initially feeds back negatively on the tonic centre. LH continues to be produced to ensure the follicles mature, and produce higher concentrations of oestrogen. There is no progesterone after the end of pregnancy, and the increased oestrogen induces a surge of GnRH from the hypothalamic surge centre, and ovulation - 49 -
occurs. The cycle continues as normal after this. Sometimes it does not, see lactational anoestrus below. On this subject, it is pertinent to broach the subject of foal heat mating. There are strong schools of thought, that the horse (mare) has been evolutionarily designed for this rapid return to oestrus, so that she can continue to be pregnant every 12 months. In young mares, typically below 12 and certainly below 10 years old, this is usually the case. Within certain criteria, foaling rates have reportedly been the same as those bred to later cycles. A subject which, in my opinion, should not be ignored.
‘Lactational Anoestrus’ This is a term used to describe mares that have foaled, and are lactating, that do not show signs of oestrus. Typically there are two presentations: 1. The mare that does not show any signs of oestrus or follicular development of more than 30mm diameter for about 30 days post foaling. 2. The mare that ovulates between 10-20 days post foaling, but then does not show any signs of oestrus or follicular development for approximately 20 days after ovulation. Although, lactational anoestrus describes the condition, it is unlikely that it is the production of milk that is causing the lack of cyclicity. Lactation does not tend to induce anoestrus in the mare, unlike other species such as the beef cow, and the pig. There appear to be some mares that are predisposed to this condition, and will do it repeatedly. Often they will ovulate and then ‘shut down’ for variable periods of time. Foal heat service is one option in mares with this history. The most likely reason for the lack of cyclicity in these mares is due to a nutriti onal imbalance or deficit. Fortunately they are not that common, which probably explains why there is no known reason for this occurrence. As would be expected, treatment options are many and varied, and include:
Foal Heat mating
Increased feeding of the mare - 50 -
Fostering the foal to a surrogate dam
Removing the foal from the mare for varying periods of time
Drug administration such as GnRH, FSH, Domperidone, Regumate ®, and intravaginal progesterone implants (especially where the mare has had an ovulation, this has been very successful).
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The ‘Problem’ Mare The main point of this section is to illustrate some of the less usual diagnostic methods that can be employed by theriogenologists, and some of the ‘newer’ treatments that will be discussed by other speakers. What exactly is a ‘problem’ mare? This is definitely not a complete set of what may be considered problem mares. Some have been dealt with previously eg. ‘lactational anoestrus’. This section is based on the fact that the stallion is not the ‘problem’. Two main categories: 1. Those that don’t cycle, or do not appear to cycle ‘normally’ 2. Those that cycle but do not go in foal a. No obvious reasons b. Have signs of endometritis
Not cycling or abnormal cycles.
Pregnancy, or pseudopregnancyIf mares are pregnant, or have had a dioestrus ovulation (pseudopregnant), they are unlikely to show signs of cycling. Transitional maresSee previous notes on ‘transitional mares’. Remembering that there is also the autumnal transition when mares are ‘shutting down’ for the Winter anoestrus. This is important for mares that have come from the Northern hemisphere to breed Southern hemisphere time. Also for those that are bred in the Southern hemisphere for Northern hemisphere foals ‘out of season mating’. Lactational anoestrus maresSee previous notes. cont/..
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In a very small proportion of these mares, the production of eCG (PMSG) from retained endometrial cups may be the reason for irregular cycles or not cycling. This may also occur after abortions or early embryonic loss. Abnormal body conditionMares that are very thin will often not cycle properly. The cause of a poor body condition is important in determining whether these mares begin cycling again. If it is due to lack of feeding, rectifying the problem can be easy. Other problems such as dental disease, metabolic abnormalities such as equine cushings disease, or age related senility require a diagnostic work up for the individual problem. Some (rarely) mares that are very fat and suffer from insulin resistance or ‘metabolic syndrome’ may not cycle. Typically they respond to dietary management. Previously administered drugs or vaccinationsAnecdotal evidence that the use of anabolic steroids and/or long term progestagens may affect cyclicity in mares after racing. ‘EQUITY’(R) Anti-GnRH vaccineThere are reports of this vaccine preventing cyclicity for life after its use. Trainers now have to sign an indemnity when using this in race mares. Ovulating off small folliclesThere are a small number of mares where the follicle ovulates at a smaller size, typically less than 30mm, than would be considered normal- usually more than 35-40 mm. These mares require close monitoring with both veterinary (ultrasound scanning) and management (‘teasing’ and observation) input. Haemorrhagic Anovulatory Follicles (HAF’s)A very small proportion of mares do not ovulate, but the follicles ‘bleed’ or luteinise. Understanding of what occurs in these mares is scant. They typically recurrently have HAF’s and it is often exacerbated by PGF2a or other, especially hormonal, treatments.
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Abnormal karyotypeThis means that the mare is not a ‘normal’ mare in genetic terms. Her genetic make-up is not perfectly female. Usually this means that there are abnormalities in the sex (X and Y) chromosomes. Instead of having two X chromosomes she has more or less X chromosomes, and/or a Y chromosome or some other abnormality of the chromosomes. With the horse genome (genetic make-up) mapped, these are likely to become more easily detected in the future. To confuse the issue, some mares with genetic abnormalities have been reported to have one or more foals.
2. Those cycling but not going in foal. No obvious reasonsThese are exceptionally frustrating mares to deal with. In thoroughbreds, the treatment options are limited by the rules of the stud book only allowing ‘natural’ mating and no assisted reproduction techniques (ART). However, a relatively recent paper reported by ‘Twink’ Allen suggested that the reason some of these mares may not be conceiving could be due to ‘blocked uterine tubes’. The mare requires PGE effects on the uterine tube, thought to be released from the embryo, to allow the tube to ‘open’ and let the embryo into the uterus at approximately 5.5 days post ovulation. It seems that some uterine tubes may be blocked by ‘old eggs’ and other debris, thereby not allowing the embryo into the uterus. Laparoscopic deposition of PGE onto the uterine tubes appears to have had a beneficial effect on mares that have had this potential problem. See ot her lecture on this procedure. Lecture 5. Other problems that may occur is lack of fertilisation, incompetent oocytes (eggs), lack of uterine tube cells (OEC’s) capable of facilitating fertilisation, a uterus unable to support an embryo, uterus not synchronised with the ovaries/ovarian hormones. Diagnosis and treatment are both difficult. In the TB, often treatment is not possible.
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Signs of EndometritisEndometritis is Inflammation of the inside of the uterus. There are many and varied reasons for endometritis, not all of which are due to Infection. There are a number of classifications of endometritis which include: acute (over a short period of time), chronic (over a long period of time), active, sub-clinical, post-partum (after foaling), bacterial, fungal, viral, mating induced, persistent and others, as well as combinations of these. Diagnosis of endometritis is usually via ‘swabbing’ of the uterus with a double guarded swabbing technique. Assessment of both cytology (types of cells present) and the culture of bacteria/fungi on various types of agar plates are commonly utilised. Other tests used include the use of specially designed ‘brushes’ for cytology, low volume uterine lavage (LVUL), High volume lavage and collecting the sediment. The use of ultrasound by detecting the presence of fluid in the uterus has assisted in defining which mares are likely to be candidates for further testing, investigations or treatments.
Diagnostic Methods: This is a short list of possible methods that may be used in the aid of making a diagnosis in the ‘problem’ mare. It is important to realise that a definitive diagnosis is not always possible for EVERY mare. Ultrasound: Palpation:
Per rectum and per vaginum.
Speculum: Blood Tests: HormonesProgesterone:
To ensure that an ovulation has taken place, a HAF has occurred, or to ensure that a CL is still not present- it has been lysed by PGF2a treatment.
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To determine if endometrial cups are still not present and producing eCG/PMSG that is affecting the oestrus cycle.
Others such as FSH, LH, Oestradiol- usually after GnRH stimulation. Possibly in future others such as leptin, kisspeptin etc. Uterine tests: Uterine swabbing-
To detect endometritis and its cause.
High or low volume for endometritis.
To determine the ‘state’ of the inside of the uterus. Assists in enabling prediction of the likelihood of a mare becoming pregnant, and maintaining the pregnancy to term. Also assists in formulating a more accurate and specific treatment plan for that individual mare. VERY Underutilised tool in my opinion.
Allows visualisation of the inside of the uterus.
Particularly useful for adhesions/blockages of the uterus. Also for visualisation of inflammation or particular abnormalities like focal scarring. Assessment of the papilla. Detection of ‘foreign’ bodies such as swab tips, and macerated foetuses. (Also has been used for AI.) Treatments: Ovulating Drugs-
Minimal contamination technique.
Uterine and systemic.
Corticosteroids- dexamethasone, prednisolone. NSAID’s- Phenylbutasone (‘bute), flunixil, indomethacin (Cualgesic)
PGF2a (cloprostenol- estrumate), oxytocin, carbetocin. - 56 -
Saline, Hartmanns, Kerosene, DMSO, Tris/EDTA (+/-
Antibiotics) Newer options: Laparoscopic PGE on the uterine tubes. See lecture 5. Laparoscopic imbrication of the uterus. See lecture 8. In animals not restricted by various breeding procedures, other more novel approaches are possible, including:
Artificial Insemination- fresh semen, extended semen, chilled extended semen, frozen semen, deep horn insemination, endoscopic insemination (sex sorted).
Oocyte Retrieval (Ovum pick up), Gamete in vitro fertilisation (GIFT).
Intracytoplasmic Sperm injection (ICSI)
Summary The ovarian cycle is just that, a cycle. Imposed on that cycle in the mare, are the periods of cyclicity, transition, and acyclicity. Knowledge of the hormonal status during cycling allows modification of the cycle lengths to enhance productivity of reproduction in the mare. There are a number of diagnostic modalities available to determine the reason/s why a mare is not becoming pregnant. There are now a few novel treatment methods, primarily involving laparoscopy, that assist in both diagnosing and treating ‘problem’ mares.
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Parturition in the Mare Lecture Three Dr, J A ROGER, BVMS, MRCVS,FACVSc Specialist in Equine Reproduction CENTRE FOR EQUINE REPRODUCTION MEDICINE, JERRYâ€™S PLAINS, NSW
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The human pregnancy was illustrated by Leonardo da Vinci in 1489
Some of the first accurate descriptions of the developing human foetus and obstetrics were done by none other than Leonardo da Vinci at the end of the 15 th Century. His excellent illustrations showed the developing foetus in the uterus, and he had some wonderful illustrations of foetal malpresentations at birth. Human dystocia was a disaster and as you will shortly see a caesarian procedure was not a great option for the mother!
Assisted births were not always successful and the history of modern obstetrics is relatively recent •
Between 1786 and 1876 not one woman survived a caesarian in Paris
In the 1880’s mortality was 92% in New York
At the same time mortality was 12.5% for slaves in Louisiana “here it was performed early in labour because there was little concern for the mother”
In a study mortality was 44% where women did sections on themselves or were gored by bulls -less than half the mortality having a physician operating in late labour!
By 1930 “maternal mortalities were less than 2% in early labour,10% in late labour, 15% after induction of labour and 27% after failed forceps delivery in the second stage of labour
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Although caesarian sections were contemplated throughout time ( the name comes from the story that Julius Caesar was born in this manner) the procedure was considered a sacrificial one to save the child. The mortality figures are horrific, 85% in Great Britain and Irela nd in 1885, 92% in New York in 1887, and 100% in greater Paris for the entire period from 1786 to 1876*. The procedures were radical, there were no antibiotics, the uterus was left unsutured until 1882 when Sanger introduced a modified procedure. This article of Sangers changed obstetrics from then on but “Sanger only reported one case and many of his ideas came from frontier medicine practiced in the United States!” * These figures are quoted from “Caesarian Section in Perspective by R.C. Burchell MD, FACO G in”New Techniques and Concepts in Maternal and Foetal Medicine”
EQUINE OBSTETRICS HAVE STEADILY DEVELOPED • Caesarian in cattle began to become routine in the 1960’s. • The first successful caesarian in a mare in Australia in 1977? • Now routine and with reasonable success rates with better control of surgical shock, sepsis and an acceptance of early intervention
Fortunately the changes were not lost on the Veterinary profession . Obstetrical procedures including caesarian sections have been absorbed, modified and wi dely accepted. Not only the radical surgical procedures such as those mentioned but the understanding of shock, the development and understanding of endocrinology, mare management and neonatal adaptation have moved in an exponential way so that we can undertake procedures that even until recently could never even be imagined
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THE FOALING MARE •
A rapid event involving major physical and physiological changes in the mare and the foal culminating in the transition from a single individual carrying a dependant parasitic offspring to two related individuals capable of moving together through the environment but with adaptations to enable the mother to support, nourish,defend and teach the newborn offspring.
• In a few hours the mare and foal will achieve physically what takes a human as many years
The take home message from that is we can still look at our counterparts in the human field and consider what our gold standards might be. In the mare everything happens very quickly. In my opinion we have at the outside one and a half hours from the time a foaling is presented to get a viable foal. At the end of this time the foal will probably have oxygen deprivation and can be expected to suffer from the some or all of the many expressions of “neonatal maladjustment” . In response to this we have seen a dramatic improvement in the quality and quantity of nursing at the foaling unit. Staff increasingly understand when to stand back and watch and when to check for problems and when to take action. Veterinary knowledge continues to increase and the veterinary practitioners have available excellent referral facilities enabling them to make those early intervention decisions in a timely manner.
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IT ALL HAPPENS SUDDENLY PREPARE FOR NEXT PREGNANCY
CHANGE IN UTERINE BLOOD FLOW
ORDERLY SEPARATION OF PLACENTA
REARRANGEMENT OF ABDOMINAL CONTENTS HORMONES OF OESTRUS CYCLE
BIRTH DROP IN PREGNANCY HORMONES
ANTIBODY ACCUMULATION IN UDDER
MATERNAL INSTINCTS SUCKLING
Parturition is not a single event but a collection of simultaneous events in several organ systems not only in the mare but also the foetus. This changes are major, of great significance, are all essential and have to be exquisitely timed. The placenta has to separate in an orderly, sequential manner , the uterus has to expel the foetus, the foetus has to be ready to become actively if not physically , independent. The mother has to adjust to supporting this free moving and sometimes too independent offspring, care for it feed it and protect it.
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WHAT CAN GO WRONG? YOU NAME IT! HERE ARE A FEW FOR STARTERS
CHANGE IN UTERINE BLOOD FLOW
HAEMORRHAGE UTERINE CONTRACTION
PREPARE FOR NEXT PREGNANCY
DROP IN PREGNANCY HORMONES
ORDERLY SEPARATION OF PLACENTA
PERSISTENT ENDOMETRIAL CUPS HORMONES OF OESTRUS CYCLE
REARRANGEMENT OF ABDOMINAL CONTENTS
COLIC, RUPTURE MILK PRODUCTION
ANTIBODY ACCUMULATION IN UDDER
NEONATAL ISOERYTHROLYSIS SUCKLING
NON-ACCEPTANCE OF FOAL
FAILURE OF ANTIBODY TRANSFER
Every single change can go wrong!
Malpresentations at Delivery The most commonly seen are;
Delivery of the foal , the ultimate act of parturition can be very rapid and forceful, especially in a young maiden. These inexperienced mares may panic and exacerbate a difficult situation. Malpresentations need to be corrected quickly and it often takes considerable experience on the part of the attendant to spot early when things are starting to go wrong. A condition seen more in maidens than in older mares is that of vagino-rectal penetration. The mare presses with undue force, sometimes before the feet are properly presented through the vulva with the result the foal’s feet will tear the roof of the vagina. This tear may be so severe as to go completely through the roof of the vagina into the rectum resulting in a recto-vaginal fistula formation. Uncorrected - 63 -
the birth will continue to completely year the perineum. Such injuries result in contamination of the vagina and cervix with faecal material leading to infertility. Other malpresentations such head-back, dorso-transverse and caudal presentations will prevent the foal passing through the pelvic canal. Delivery requires manipulation and correction. Such procedures may require sedation and anaesthesia and in extreme cases may require a caesarian delivery. It is also noteworthy that the latter two may not be presented at the vulva or in the vagina.. This means that those foaling alarms relying on vaginal presentation may not be set off. The ‘sitting dog” presentation may be mistaken for a gross oversize as the foal cannot be del ivered although both front feet and the head are presented. The foal cannot be delivered because the hind feet are up against the pelvis. Correction of this malpresentation is extremely difficult. Forced traction can damage the mare. The outcome of these cases is rarely good often resulting in the death of the mare or the foal or even both.
MALPRESENTATIONS at Delivery HEAD BACK
The “head back” presentation requires the foal to be repelled back into the birth canal and the head to be brought up with the nose presented with the feet. This can only be readily achieved with a relaxed uterus as the oxytocin-powered uterine contractions will be working against any attempt at correction.
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MALPRESENTATIONS at Delivery LEG BACK
To correct a “leg-back” presentation the head and foot will need to be repelled and the backward leg brought forward. This is usually done by flexing the carpus first and then carefully bringing the fetlock up. Care should be taken not to cause a uterine tear with the foot.
MALPRESENTATIONS at Delivery DORSO-TRANSVERSE
This presentation is virtually impossible to correct and usually requires a caesarian section. Fortunately it is not common.
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MALPRESENTATIONS at Delivery CAUDAL (BREECH)
Breech presentations are sometimes seen as a tail only, or nothing presented. The foal needs to be repelled ad the hind legs brought up . The foal is then delivered hind end first. Because the placenta usually separates as the foal is presented these foals asphyxiate quickly. A fast delivery is needed to be save these foals and the procedure is often unsuccessful.
MALPRESENTATIONS at Delivery â€œSITTING DOGâ€?
This is one of the hardest malpresentations to correct and is often misdiagnosed as a foetal oversize. Correction requires the toes to be repelled and held back while the foal is delivered. - 66 -
Failure to repel the toes during delivery will result in a fatal uterine tear.A caesarian section may be necessary.
MALPRESENTATIONS at Delivery VAGINO-RECTAL PENETRATION
Known mostly as a “recto-vaginal fistula” this is most often seen in maidens but may also occur in older mares if a caslicks procedure has not been opened. Although the feet do the penetration the delivery may be with the feet protruding through the vagina but the head through the rectum. This is because the foal retracts and represents the feet during delivery .Amazingly the foals often survive but surgical correction is necessary before the mare can breed again. Small tears can sometimes be corrected soon after foaling but major lacerations need to be left for several weeks until the inflammation and tearing settles before surgical repair is possible.
Quote W.R.McGee,Founder of Hagyard Davidson McGee, Lexington. The Stud Managers Course, Kentucky 1962
“If I were limited to talking to you on this particular subject to just 10 seconds I would say this - DO NOT RUSH A FOALING MARE! and having said it I could sit down feeling I had made a useful and informative contribution”.
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The Road to a Healthy Foal Preparedness For Birth
First Foal History
Other Techniques Genetic Makeup
Foal Haemolytic Diseases
Growth Rate Multiple Birth
Size For Age
Similarly for the foal transition to being a foal from a foetus is the culmination of a complex series of multiple changes that are inter related and sometimes independent but all have to be achieved at the same time. Dramatic changes have to be made to the cardiovascular, respiratory, digestive, locomotor and proprioceptive systems, and all within a time span of a few minutes to a few hours at the most.
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DRAMATIC PHYSIOLOGICAL CHANGES IN THE FOAL Dramatic changes are seen in :Circulation Lung Function Thermoregulation Brain Function Pancreas And Digestive Tract Cartilage
At birth the foal suddenly-within a matter of minutes â€“ has to completely change its physiological structure to move from a dependant life supported by the mare to an independent sys tem. This involves not only changing a foetal circulation system that obtains oxygen and nutrition via the placenta and disposes of waste through that structure but establishing a circulatory system that will collect oxygen and expire waste gases including carbon dioxide, will pass blood through the digestive tract for nutrition and further waste disposal but will include increased renal function. The lungs are required to expand and to do this they must produce surfactant to reduce surface tension that would otherwise stick the sides together preventing air flow. As air starts to come in from outside a new immune and disease prevention system has to come into play as the lung is exposed for the first time to toxins, pollution, and infectious agents. The chest must reliably start to expand and contract and continue to do so for the rest of the horses life. The respiratory centre of the brain has to become responsive to carbon dioxide tension in the blood to stimulate breathing. Note it is the presence of carbon dioxide in the blood that stimulates breathing, not oxygen requirement directly. Once the oxygen supply and the removal of carbon dioxide from the foal is cut off by placental separation the foal must breathe independantly. Oxygen supplementation alone will not get a foal to start breathing, but a quick blow of expired air from the attendant might be helpful as it contains carbon dioxide. Use of a whole air ressuscitator is good. However the pathology of the condition called neonatal maladjustment system is oxygen deficiency which is why it is now often referred to as an ischaemic-anoxic condition.
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The foal also has to start to maintain its own body temperature and newborn foals will rapidly become hypothermic. Work in lambs which studied twins and also compared maternal body condition showed that offspring from ewes with good body condition initiated shivering and homeostatic responses quicker. Brain function shows rapid response to birth varying from endocrine gland function to proprioceptive appreciation of the surroundings. This includes the all-important bonding with the dam, seeking the udder and initiation of a fear-protective response. Standing, balance,sense of smell are all rapidly put to work. We like foals to suckle as soon as possible. This already said requires a bonding and sucking reflex but requires changes in the gastrointestinal tract structure and function. Endocrine and exocrine glands of the gastrointestinal system have to come into play. Insulin resistance and delayed pancreatic function may be a normal feature of the newborn. Interesting work is being done on skeletal function in the newborn foal. The cartilage of the foetus is different from that of the foal and some fundamental changes take place as the foal enters the free world with possible demands of extreme exercise that might be life-saving.
FOAL WATCH Supervision Of A Natural Process Avoid Interference Unless Necessary- Iatrogenic Conditions! Knowledge And Understanding Of The Process Understand The Difference Between Assistance And Interference The Importance Of Records
A successful foal watch person understands they are there to supervise a natural process and to be on hand should problems arise. It is important to allow the process to go unhindered whenever possible. Particularly in maiden mares there is a fine line as to when to allow birth to proceed uninterrupted and when to help. The stimulus for mothering in the maiden mare is partly from the release of oxytocin as the foal - 70 -
passes through the canal. Once the foal is born the maiden mare may be put off accepting her foal by the attentions of an over enthusiastic human being. Excessive interference has become a bit of a fashion as people try to demonstrate their enthusiasm by “getting in there” too soon. Over the years I have seen what we call “iatrogenic” conditions arise in this way. Infections, tears are sometimes seen. Malpresentations with a head back can be caused by pulling on legs before the head is presented in the pelvic canal. Umbilical hernias may be caused by the mare getting up too soon ,pulling at the cord as it passes through the foals umbilicus. The resulting local haemorrhage will prevent the abdominal wall from completely closing, resulting in a gap which will appear as a hernia. There has been a recent fad, particularly in America to try to feed the foal a small amount of colostrum from a bottle as soon as it is born. I consider this practice as an un necessary nonsense unless you anticipate a neonatal isoerythrolysis in which case colostrum from a “safe” mare is needed. Particularly with maidens , my opinion is they need time to bond to their foal and are best left alone to work out what this little creature is and what to do with it. The foal also needs to recognize its mother and to go there for food and protection, and comfort. The importance of records can not be understated. This enables you to see what is going right, look back to see where things may have gone wrong and enable you to have an overvi ew of the stud s procedures. They will also be important in the case of a dispute. AVOID EXCESS Do not compete with other studs to introduce the newest crazy idea under the guise that you are doing something better or special!
IGNORANCE IS BLISS • Do What You Know, Not What You Think Will Impress Others • Listen To Experienced (Not Necessarily Self Taught) Operators And Be A Sponge For Good Information
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Common Diseases in the first three days Lecture Four DR NIAMH COLLINS, Diplomate ECVIM Clovelly Intensive Care Unit, Scone Veterinary Hospital
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Introduction Over the last 20 years there have been large developments in the treatment and management of a sick foal so that the old belief of a “sick foal is a dead foal” is no longer true. Many studies have highlighted that the quick early recognition of the sick foal and subsequent early aggressive treatment is critical to a successful outcome. Recognis ing the “high-risk pregnancy” and being prepared for the birth of a compromised foal is also essential. The following article outlines problems that may indicate the birth of a potentially compromised foal, how to detect an abnormal foal and some of the more common neonatal diseases. Careful monitoring of the pregnant mare is essential to detect any problems which may be occurring with the pregnancy. Any systemic illness the mare has during her pregnancy such as colic, diarrhoea or laminitis may have an impact on the foetus and result in the birth of a weak, compromised foal. Mares showing clinical signs of an abnormal pregnancy may also produce a potentially compromised foal. The most common abnormal clinical signs seen during pregnancy are a purulent vaginal discharge and premature lactation or udder development, which are clinical signs of placentitis. The infection in the placenta can spread and cause an infection in the foetus. The placenta may also be compromised and therefore not provide adequate nutrition and oxygen to the foetus. A mare with a previous history of an abnormal delivery or problem pregnancy should also be monitored closely as she has an increased likelihood of producing another compromised foal. The identification of a potential problem with the pregnancy and the high possibility of a compromised foal being born should alert stud personnel and the veterinarian so there is closer monitoring of parturition and the newborn foal and there is potentially earlier detection of neonatal illness… the key to a successful outcome.
The Normal Foal It is important to know the normal behaviour and parameters of a neonatal foal so the subtle abnormalities of a sick neonatal foal can be detected (Table 1). A normal foal after birth should be immediately active and trying to support its head and sit sternal. The foal should be responsive and touching the foal’s nostrils and ears should evoke a brisk response. The foal should develop a - 73 -
suckle reflex within 20 minutes of birth. This can be assessed by placing a clean finger in the foal’s mouth. Shortly after birth the foal should be attempting to stand and should be able to stand and nurse from the mare within 2 hours. The foal may need some guidance to find the teat and some mares may need to be restrained so the foal can nurse. This first nurse of colostrum is very important to the foal’s health as the foal is born without any immunoglobulins and relies on the absorption of immunoglobulins and other factors from the colostrum to help prevent disease. After nursing the foal should pass meconium and then lie down and sleep. The foal should subsequently get up readily and nurse about every 30 minutes. When awoken the foal should get up, stretch and then go to nurse. It is very important to bend down and watch the foal nurse, ensure it has a good tongue seal (Figure 1) and no milk is coming out of its nostrils. A sick foal may stand under the mare and look as though it is nursing but not be sucking from the teat. Many of these foals have “milk staining” of the face which is an early sign of a sick foal. Foals which are not nursing can have failure of passive transfer, become dehydrated and hypoglycaemic. After nursing the foal should urinate (if it didn’t prior to nursing), be inquisitive, investigating the surrounding area and then lie down to sleep. Foals which do not do this are most likely to have a problem. Some sick foals forget how to lie down and fall asleep on their feet. Limb abnormalities such as tendon laxity or contracture limit the foals’ ability to stand, nurse or walk and will need further veterinary attention. Common neonatal diseases There are unfortunately many diseases the newborn foal can succumb to. The most common diseases which are seen are septicaemia, Hypoxic Ischaemic Syndrome and prema turity. Many of the diseases of the neonatal foal can occur together and are often a result of placentitis. The more common diseases encountered are outlined below. Hypoxic Ischaemic Syndrome (“Dummy” foal) Neonatal Maladjustment Syndrome, dummy foal, wanderer, barker foal, perinatal asphyxial syndrome are all other names for Hypoxic Ischaemic Syndrome (HIS). This disease is currently thought to be caused by the lack of oxygen supply (hypoxia) and poor blood perfusion of tissues (ischaemia) of the foal which can occur either during pregnancy, during parturition or shortly after birth. Our current knowledge on the disease has been extrapolated from human medicine and - 74 -
experiments in other species. The severity and types of clinical signs depends on what organs are affected and on the length of time and severity of the oxygen deprivation and poor tissue perfusion. The most common organ systems involved are the brain, kidney and gastrointestinal tract, although any organ can be affected. Placentitis, placental insufficiency, general anaesthetic of the pregnant mare, dystocia, C -section and premature placental separation (red-bag delivery) are all potential causes of HIS. The disease can also occur from apparently uncomplicated pregnancies and deliveries, so there is still more to learn about the different causes of this disease. After the foal is born problems such as neonatal isoerythrolysis, fractured ribs, pneumonia and prolonged recumbency from contracted tendons can lead to the development of HIS. The clinical signs may be present at birth or develop over the next 3 days and will depend on the organs involved. The clinical signs of brain involvement vary from milder clinical signs such as lack of affinity for the mare, lack of suckle reflex, inability to find the udder or hyper-responsiveness to more severe signs: irregular respiratory rate with periods of not breathing and convulsions. Foals may have abnormal vocalisation (barkers), although this is not common. If the kidneys are affected, foals may show signs of renal failure (development of oedema, produce urine at an inappropriate concentration). Gastrointestinal tract involvement may be seen as mild colic or in more severe cases the foal may display signs of septic shock, severe colic with blood discoloured diarrhoea. Treatment depends on the organ systems involved and severity of the clinical signs and is aimed at supporting the foal until the damaged tissue heals. The treatment may range from placing an indwelling stomach tube so the foal can be fed until a suckle reflex develops, to intensive therapy of intranasal oxygen (Figure 2), intravenous fluids, parenteral feeding (providing intravenous nutrition) and anti-convulsant therapy. The majority of foals (>90%) with neurological signs recover and are normal adults and athletes. If other organs are affected the recovery depends on the severity of the damage and the organs that are affected.
Prematurity The reported gestational length of the mare is from 320-365 days, however there are reports of mares which produce a normal foal at 305 or 410 days of gestation. This highlights that all mares - 75 -
have their own gestational length. So if a foal is born from a mare at 305 days, the foal is “normal” for the mare that has a normal gestational length of 305 days, but 4 weeks premature for a mare whose normal gestational length is 335 days. So a “premature foal” is one which is delivered before the due date of the mare. A dysmature foal is born on time for the mare however the foal hasn’t received the nutrition it needs to grow and is born looking like a premature foal. These foals have similar clinical problems as premature foals. The most common cause of a premature foal is placentitis. Other causes include early removal of a foal due to severe maternal illness, twins and induction of parturition based on calendar dates rather than the foal’s maturity. Premature foals have a classic soft silky hair coat, are small, have floppy ears, domed forehead and increased tendon and joint laxity (Figure 3). The internal organs of the foal are also “premature” so often the lungs, gastrointestinal tract, kidneys and glucose regulating systems are not functional. These foals also have incomplete ossification of their cuboidal bones (Figure 4a & b). The immature bones are easily crushed and damaged if the foal has too much exercise or gains too much weight. Treatment options for a premature foal range from supportive care to very intensive therapy of mechanical ventilation, intravenous fluids and parenteral nutrition. The foal will also need to be confined until there is complete ossification of the cuboidal bones (as determined by radiographs). Their legs also need to be carefully monitored for any angular limb deformities. The unborn foal that has been subjected to in utero stresses, which occur with a chronic illness of the mare or a placentitis, have had their maturation hastened and are often born with mature lungs and hormone regulation. These foals have a better chance of survival and thus it is possible for foals to be born as early as 280 days of gestation and survive. A foal which has been removed from the in utero environment before final maturation of the organ systems has occurred (such as with a terminal C-section in a mare with a broken leg) has an extremely poor to hopeless prognosis for life.
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Septicaemia Septicaemia is a term used to describe a generalised systemic infection within the blood stream and may involve multiple organs. The infection may then localise into an area and cause an infection in the lung (pneumonia), gastrointestinal tract (enteritis), joint (septic arthritis), bone (osteomyelitis) or other area. Septicaemia is the leading cause of death in neonates. The foal can become infected before it is born (via a placentitis) or after it is born. This occ urs most commonly by the foal ingesting bacteria in the first few hours of life when it is finding the udder to nurse or investigating its environment. Infection by bacteria can cause mild clinical signs such as dullness and decreased nursing, or can set off a cascade of reactions in the foal which can result in shock and death. It is thus imperative the infection is detected early and appropriate aggressive treatment begun. In some cases however even this is not enough to save the foal. Treatment of these foals depends on the severity and location of the infection. Bacterial septicaemia is treated with antibiotics. Intravenous plasma may be used to improve the foalâ€™s immunity and other therapies such as intranasal oxygen, intravenous fluids and drugs whic h improve the blood pressure and tissue perfusion may be utilised. Ensuring the foal has an adequate immunoglobulin concentration (IgG) of > 8g/L, avoiding overcrowding and ensuring clean dry foaling and newborn areas are critical in trying to prevent septicaemia. Unfortunately even if all these precautions are taken, a foal may still develop septicaemia. Diarrhoea Diarrhoea in the neonate is common and in the foal less than 3 days of age it is most commonly associated with septicaemia. The episode of diarrhoea can be mild and self limiting or life threatening with severe sepsis as seen with clostridial infections. Common signs include fever, depression, dehydration and not nursing. Often signs of colic are present, even before the foal develops diarrhoea. Many therapies used in the treatment of diarrhoea are similar regardless of the cause. Restoring circulatory volume and correcting dehydration, electrolyte and metabolic abnormalities are essential. Intravenous fluids and electrolytes are used in more severe cases. Oral fluids and - 77 -
electrolyte supplementation is used in mild to moderate dehydration where there is a functional GIT. Plasma is often used if hypoproteinemia is present and it also provides immune factors. Antibiotics should be used in foals < 7days old due to the infectious aetiologies and high risk of translocation of bacteria. Nutritional support is an important part of management of the foal with diarrhoea as many foals respond to milk restriction. Foals with abdominal distension and colic s hould be withheld from feeding until these signs resolve. They however need intravenous fluid and glucose supplementation whilst their access to the mare is restricted. Parenteral nutrition (TPN) maybe utilised if more prolonged gastrointestinal rest is needed. There are a variety of other therapies such as kaolin/pectin, bismuth subsalicylate, sucralfate and probiotics which are used in the treatment of diarrhoea in the young foal. Their use will depend upon the clinical experience of the veterinarian and stud personnel. The use of antiulcer medications is debatable, however use is recommended in older (> 7 day old) foals. Supportive therapies such as regular cleaning and application of protective cream and fly repellants over the rump and vulva are important. Strict hygiene and isolation protocols should be adhered to when treating foals with infectious diarrhoea. Often diarrhoea is part of a farm problem thus, where possible, control and preventative measures on the farm should be instigated. Meconium impaction Meconium is the first manure a foal will pass. It consists of amniotic fluid and cellular debris that is swallowed during the foalâ€™s development in the uterus. The meconium is brown olive green in colour, firm to hard consistency and is usually passed within the first 24 â€“ 36 hours after birth. The meconium may become impacted in the rectum, or small or large colon. The foal may have already passed some meconium prior to signs of an impaction developing. The foal may show clinical signs of colic (rolling, kicking at belly, lying on back), straining to defaecate, wander around aimlessly or go to the udder but not nurse. The signs of colic usually occur just after the foal has just nursed. Treatment involves administration of an enema, oral drench of paraffin oil, administer intravenous fluids and/or pain relief. Some impactions may need to be treated surgically; however this is extremely rare if the impactions are treated early.
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Ruptured bladder A ruptured bladder or uroperitoneum (urine in the abdominal cavity) can occur in both colts and fillies. The defect in the urinary tract not only occurs in the bladder but can occur anywhere from the urachus (tube connecting the bladder to the amniotic sac while the foal is in utero) to the ureters (tubes from the kidney to the bladder). It has traditionally been thought to occur more commonly in colts and occur during the foaling process however recent reports have highlighted the condition is just as common in fillies and may also occur after parturition. Foals with uroperitoneum are usually normal at birth and may urinate normally. Classically the foals strain to urinate and produce small amounts of urine; it should be noted however that foals with colic can also display these symptoms. The foal’s abdomen will also begin to increase in size with the increasing accumulation of urine. As the foal can not get rid of the urine out of its body, it begins to absorb the waste products from the urine and develop abnormal electrolyte abnormalities, in particular high potassium concentrations (an electrolyte which is high in urine). The abnormal electrolyte concentrations can become life threatening. The foal needs surgery to repair the defect in the urinary tract. However the foal’s electrolyte levels need be stabilised first with intravenous fluids and drainage of urine from the abdomen. Once the defect is repaired the foal has a good prognosis. Neonatal isoerythrolysis Neonatal isoerythrolysis (NI), also referred to as “jaundiced foal or haemolytic foal” occurs when the foal ingests colostrum from the mare which contains antibodies against its own red blood cells. The antibodies destroy the red blood cells which results in anaemia and an increase in bilirubin (a product of red blood cell break down) which causes the jaundiced or yellow appearance of the foal’s gums (Figure 5). The mare develops antibodies by being exposed to the blood of a previous foal (such as during foaling or with a placentitis) or having a previous blood transfusion. The foal is affected if it has inherited the blood type from the stallion which the mare has produced antibodies against. There are many different blood types of horses, unfortunately the 2 most common types are the most common involved in NI.
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The clinical signs vary depending on the severity of the destruction of the red blood cells (haemolysis). The foal is normal at birth and then can develop symptoms within 6 hours or until around 7 days of age. The longer the clinical signs take to develop the less severe the haemolysis and clinical signs. The clinical signs range from an increased respiratory rate and jaundiced (yellow) mucous membranes to recumbency and seizures. The treatment depends on the severity of the clinical signs, and some foals with the most severe form of the disease can die despite intensive therapy. Some foals may require intranasal oxygen therapy and a blood transfusion; other foals may just need careful monitoring. The disease can be prevented in mares which are known producers of foals with NI. The newborn foal should not be allowed any access to the mare and receive its colostrum from another source. The mare should be milked out for 36 hours and the milk and colostrum discarded. The foal should be fed supplementary milk for 36 hours. After this period of time the foal can then nurse from the mare. Umbilical problems The umbilicus or navel needs to be closely monitored for the first few weeks of life. Shortly after birth the umbilicus should be moist but have no excessive bleeding. The umbilicus should be carefully disinfected shortly after it breaks and twice daily for the first 2-3 days after birth. Dilute disinfectants such as 2.5% iodine are recommended, anything stronger may be caustic and lead to tissue damage and necrosis. The solution is best applied with a s mall spray bottle, spraying the umbilicus but avoiding the surrounding skin. The umbilicus may become infected which is usually seen as moistness, tenderness to touch, presence of swelling and purulent discharge. Sometimes the internal part of the umbilic us may become infected and there is no obvious external sign of swelling or infection. Ultrasound examination will be able to visualise the infected remnants. The umbilicus may also leak urine (patent urachus) as it contains the urachus. The majority of foals with a patent urachus or infected umbilicus will respond to medical management of antibiotic therapy and keeping the foal in a clean dry yard or small paddock. Previously surgery was recommended however now it has been found that the majority of these conditions resolve with medical treatment alone. - 80 -
Entropion This occurs when the eyelid, most commonly the lower, rolls in. It can be present at birth or occur after birth and is usually associated with prematurity, dehydration, or generalised muscle weakness. The hair from the eyelid then rubs on the cornea and, if left untreated, results in a corneal ulcer. This can be a very serious condition and can result in loss of the foalâ€™s eye. If an entropion is seen, the eyelid can be manually rolled out or tempo rarily sutured out, and the eye examined to assess if an ulcer has formed. Corneas are less sensitive in foals, thus ulceration can be present without evidence of pain and fluorescein staining is needed to highlight the ulcer. Treatment may involve topical broad-spectrum antibiotic therapy, though severe deep ulcers may require surgical treatment. As highlighted above the key to a successful outcome is careful monitoring of the newborn foal so there is early detection of any illness. This will allow the ins tigation of early and aggressive treatment. Treatment of the critically-ill neonate is time and labour intensive thus referring your foal to an intensive care unit which will have the nursing, veterinary staff and expertise to provide 24 hour intensive care for the foal should be considered.
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Normal newborn foal
Abnormal newborn foal Dark reddish pink
Pink and moist
Purple or yellow tinge Small haemorrhages Laboured respiration
Regular. 60-80 breaths/min at birth. Respiration
Decreases to 20 - 40 breaths/min within 1 hour of birth.
Exaggerated chest and abdominal movement Nostril flaring with breaths
80-100 beats/min after birth. Can Heart rate
increase to 150 beats/min with struggling and attempts to stand.
37.5 - 38.5oC
Not reliable indicator of infection
Sitting sternal after few minutes
Not sitting sternal after birth
Standing and nursing within 2 hrs
Not standing/nursing within 3 hrs
White, moist in new born Leaking urine
Urinate within 12hrs of birth
Straining to urinate
Table 1: Parameters of a new born foal
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Figure 1. Foal nursing showing good tongue seal on teat. Foal also has an indwelling nasogastric tube through which it had been fed until it developed the good suckle.
Figure 2. Intranasal oxygen therapy utilised on a recumbent foal with lack of tongue control, a common finding in foals with HIS. - 83 -
Figure 3. Premature foal highlighting domed forehead, floppy ears, small size, and thin silky coat.
Figure 4a and b. Radiographs of a hock and carpus from a premature foal with incomplete ossification.
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Figure 5. Foal with pale yellow mucous membranes from neonatal isoerythrolysis
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Foal conformation & Uterine tube assessment and PGE deposition in mares Lecture Five Dr ANGUS R ADKINS, BVSc FACVSc Specialist in Equine Surgery Scone Equine Hospital - 86 -
Limb Conformation and Methods of Correction in Foals Introduction This article has been written to provide you with a summary of foal conformation – the anatomy and how growth occurs, causes of conformational faults, the definition of conformational faults, how to assess conformation in foals and the treatment options. The lecture I give will be an interactive presentation to show you the types of conformational faults seen, how to assess these and what methods of treatment are available. Conformation is a commonly evaluated component of any potential athlete. Some believe certain conformational traits can have an effect on a horse’s potential speed and that horses with a certain conformation have a better chance of being sprinters or stayers. These are the traits often evaluated by buyers at yearling sales and thankfully there are differing opinions as to the ideal conformation, thereby allowing the sale of all types of horses. The consideration of body type is beyond the scope of this lecture and I will concentrate on lower limb conformation as this is an area we can potentially manipulate to correct perceived faults. I doubt lower limb conformation can significantly affect a horse’s potential speed, but it can certainly affect a horse’s chance of developing lameness, thereby affecting its speed and performance. Certain conformation traits have been shown statistically to increase a horse’s chance of developing ligament injuries, knee chips and inflammation of fetlocks and knees. Many critics of surgery to correct limb deviations are of the opinion this is being done purely to increase a horse’s saleability. This is one reason, but I have no doubt a horse with good conformation has a better chance of racing earlier in its career, for longer, and with fewer interruptions to its training program. This can significantly impact on the cost of training a horse. Lower limb conformation can certainly be manipulated by non-surgical and surgical means and a thorough understanding of these techniques should be known by all staff on stud farms. These is a “window of opportunity” to allow manipulation of limb conformation, and if this window is lost, permanent conformational faults will result. Manipulation can only be undertaken if a fault is first recognised and brought to the attention of the manager, farrier or veterinarian. As such, the principles of anatomy and growth, causes of faulty conformation and the recognition conformation faults must first be known. This will allow a better understanding of the techniques - 87 -
for manipulation of limb conformation. This lecture will cover these basic principles before expanding to discuss the techniques for manipulation of lower limb conformation.
Anatomy An animalâ€™s shape is basically dependent on its bony skeleton. The skeleton is supported by soft tissue structures, such as tendons and ligament. Horses are born with a complete but immature skeleton and it is the growth of the bones and soft tissues that allow the development of its adult shape. Bone growth occurs in a number of locations along any given bone. The physis or growth plate (see Figure 1) is where the most elongation to bone length occurs and it is here where the most significant change to conformation can occur. Growth plates close at some point during ageing, thereby stopping any significant lengthening of that particular bone. In general terms, the closer to the ground the earlier the growth plate closes. For instance, the growth plates at the fetlock are closed by 6 months of age, but the growth plates at the knee are not closed until about 18 months of age. As such, any conformational fault at the level of the fetlock cannot be significantly improved after 6 months of age, but any knee conformational fault can still be improved as a yearling.
Figure 1: Xray image of a foalâ€™s knee There is a screw on either side of the physis or growth plate. Notice the growth plate is horizontal and perpendicular to the long axis of the bone. It is somewhat irregular in outline, compared to the three joints that are below.
Bones grow by first forming cartilage which is then turned into bone, basically by the laying down of calcium. Cartilage is relatively soft and can be crushed by excessive weight bearing. We know - 88 -
that a horses basic skeletal outline is formed early during pregnancy but that the initial cartilage structure is only changed to bone during the last 2 months of pregnancy. As such, if a foal is premature, or under-developed due to a placentitis, it will be born with a lack of bone. The poorly developed skeleton, being composed of too much cartilage, will be weak and prone to crushing and the development of limb deviations. We know that the horse bears most weight down the inside of the limb, and for this reason, if a foal is born with an immature skeleton a toe-out or valgus deviation will often result. The growth of soft tissues is not as easily explained, however, a balance between bone growth and soft tissue must occur to allow normal conformation. Flexural deformities, such as “over at the knee” or “club feet”, may be a consequence of an imbalance between soft tissue and bone growth. Foals tend to have their fastest growth rate at birth, which then slows during ageing. As a foal ages the growth rate becomes more sporadic with periods of fast growth and periods of slow growth. This may be related to stages of maturity (i.e. at yearling age), nutrition or fol lowing illness. Regardless of the cause, some manipulation to overall growth rates can be undertaken, thereby changing conformation. Most methods to alter limb conformation work by affecting the growth plate, either slowing or increasing growth on one particular side of the growth plate. Knowing that foals grow fastest at birth and during the early stages of life, it holds true that any change to limb conformation occurs faster early in life.
Causes of Conformational Faults The causes responsible for conformational faults include unbalanced nutrition, placentitis or conditions that affect the mare’s ability to properly develop her foal (eg heavy worm burdens or illness), prematurity, excessive exercise or trauma and genetics. The role of genetics is not we ll documented but I have no doubt conformation is greatly influenced by the sire and dam. Their conformation is not necessarily carried forward to the foal but certain conformational traits are commonly seen in the progeny from certain mares and stallions. The relative importance of the stallion compared to the mare is not known and the influence each has, and how this is influenced by the other possible causes, is very complex and poorly understood.
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Definition of Conformation Limb conformation is described when either looking from the front or the side. When viewing the horse from the front any deviation that does not allow essentially straight alignment can be identified (eg toe-in or vaus deviations). These are Angular Limb Deformities and what we will concentrate on in this lecture. When viewing the horse from the side any deformity that causes abnormal angulation to the joints is identified (i.e. â€œback at the kneeâ€?). These are Flexural Limb Deformities and beyond the scope of this lecture. Angular limb deformities can be broken-up into three main types. It is important to understand each type as the treatment for each type is somewhat different. 1. Valgus/Varus Deviations: This refers to a true deviation that occurs at a joint when viewing the limb from the front. If an imaginary line is drawn down the middle of the limb and an angle to the line is identified, this is either a valgus or varus deviation. A valgus (see Figure 2) refers to an outward deviation and a varus (see Figure 3) refers to an inward deviation. Normally conformed foals are born with a mild valgus deviation at the knee and this will self-correct with age. Valgus and varus deviations are the most easily manipulated deviations in foals. Figure 2 Note the deviation in the black line drawn down the centre of the bones above and below the knee. This is a valgus deviation. The location where the two black lines intersect is the location of the deviation â€“ in this case, the growth plate associated with the knee.
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Figure 3 This is a varus deviation that originates from the growth plate at the knee.
2. Rotational Deviations This refers to a rotation of the limb (outwards or inwards) and NO abnormal deviation to the imaginary line mentioned earlier. Most foals are born with mild outward rotation of their limbs which self-corrects with age. This results in you having to view the foal somewhat from the side, and not directly in front of them, to be truly looking at the front of the lower limb joints (see Figure 4). The distinction between valgus/varus and rotational deviation is very important as corrective farriery or surgery to correct rotational deviations is very unrewarding, and any attempts at treatment may be harmful to the long-term soundness of the horse. Figure 4 This horse has a rotational deformity of the right front limb. At first glance the limb appears to have an outward deviation, but when imaginary lines are drawn along the centre of the bones there is only a mild valgus deviation at the knee, which is normal in young foals. There is a rotational deviation and mild valgus deviation of the left front limb
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3. Offset Deviations This refers to “offset knee” conformation with the most common fault being that the top of the canon is set to the outside of the lower knee joint. Commonly, an outwards “tilt” to the knee is also seen at this location(see Figure 5). There is no treatment that can effectively alter this conformation. However, recognising this conformation is important as foals with offset knee conformation are more prone to developing fetlock varus conformation and lameness. Figure 5 This is a “tilted” knee. Note the black lines drawn down the centre of the bones above and below the knee are in line, but the bones of the knee are at an angle.
How to Assess Conformation The assessment of conformation should start at birth. Once a foal has been delivered and it has been evaluated for more life-threatening problems, such as septicaemia or dummy syndrome, a non-invasive examination of its limbs should be done. This is done to ensure the foal is viable and there are no major problems that may suggest it will need assistance to even stand or need immediate treatment (i.e. such as splinting). Once standing, a more thorough examination of the foal’s conformation should be made. It is difficult to get a real appreciation of a foal’s conformation until it is standing and bearing weight. Weight bearing will signific antly exacerbate any angular or flexural deformities that can be identified when the foal is lying down. Any abnormalities, including their type, location and severity should be recorded.
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It is common practice for an insurance examination to be undertaken at 24 hours of age. This examination requires the veterinarian to examine the foals conformation and record on the certificate if there are any “significant angular or flexural deformities”. A significant deformity is one that may require any form of treatment, including prolonged stall confinement, splints, or surgery. This examination is a good time for managers to examine the foal with the veterinarian to identify conformational faults, and determine which ones are likely to need treatment. The foal’s conformation should be recorded. In my opinion, one of the most important factors in determining whether a foal needs specific treatment for conformational faults is the change in conformation with time. If a conformational fault is improving then I am more willing to do nothing, but if the conformational fault is static or worsening then treatment is often needed. On farms with a large numbers of foals you cannot rely on memory to determine if the conformation is changing and the recording of detailed findings is needed. Although a number of conformational faults are present at birth there are many that develop with age. A foal may be normal at 24 hours of age but have significant abnormalities by 2 weeks of age. Conformation can change, for the better or worse, very quickly and regular evaluation is needed in the first few weeks of life. A good time to do this is during the veterinary breeding examinations of the mare, a time where the foal is moved from its paddock to usually a flat, dry area where a more thorough examination of conformation can be undertaken. This system is convenient but some faults are easily overlooked in the rush to get things done. In my opinion a designated time should be made to assess the foal’s conformation on a weekly basis initially, and then less frequently as they age, with the time interval dependent on their conformation. The foal can also be assessed for other abnormalities at this time (eg weight gains). When assessing foals conformation I like to look at them on a flat, hard surface walking next to their dams. A 3 x 20 m concrete alleyway is ideal. Most foals resist being handled by pulling away from the handler, which can hide or worsen a conformational fault. Assessing a foal at rest is not sufficient either, as many conformational faults are more easily seen during movement and weight bearing. The foal should be assessed when it is walking towards and away from you. I assess the limbs for valgus/varus, rotational and offset conformation faults as well as the location and severity of the deviation. The foot is also assessed for its shape and whether corrective farriery has been undertaken. The foals type and weight is also assessed as it is usually harder to correct - 93 -
heavier foals. In order to allow a quick and consistent recording of my findings, I assign a numerical grade to the severity of the deviation and use abbreviations for the type and location of the deviation. Following is a summary of my grading system, which is not universal but commonly used in the Hunter Valley. Valgus/Varus:
+ ( positive)
Severity of deviation: 1- 4 (1 being mild and 4 being very severe) Left (near) fore:
L or LF (fetlock)
Right (off) fore
R or RF (fetlock)
Left (near) hind:
L or LH (fetlock)
Right (off) hind:
R or RH (fetlock)
For instance: A mild left fore fetlock varus deviation:
â€“ 1 VLFF
A severe left knee valgus deviation:
+ 4 VLK
A moderate outward rotational deviation of the left fore
+ 2 RLF
An moderate offset left fore knee deviation
+ 2 OLK
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At the first examination I record the mare’s conformation and breeding of the foal. I believe there is a strong genetic influence with conformation and knowing the mare’s conformation and sire of the foal can help to identify the foal’s likely conformation, and what treatment is also likely. Other factors that should be considered when assessing conformation are the magnitude of confinement and the extent of recent exercise. Changes to exercise regimes prior to examination can temporarily alter a foals conformation and care must be taken in assessing a foal after strenuous paddock exercise, floating or prolonged stall rest. Once you have learnt to evaluate conformation you must then learn when treatment may be required and what treatment options are available. There is a “window of opportunity” to allow effective treatment and if the foal is presented when it is too old, then permanent conformation faults will remain. In my opinion, the most appropriate treatment and its timing is best guided by the change in conformation with time. I believe I can make a much better decision on treatment if I have the chance to assess conformation on a weekly or fortnightly basis from 10-14 days of age (Please note: foals with severe conformational faults should be examined much sooner than this). My preference is to examine all foals with conformational faults in the way described, and then assess at what time interval I would like to examine these foals again. For those of you for which I have undertaken this process many will know my preference for treatment, and present the foal once you think treatment is needed. I accept this process can save some money, although it is not my preference as my treatment options and their timing are changing as we get to evaluate our results each year.
Treatment options 1. Exercise Restriction Once assessed at birth the level of exercise a foal is allowed should be evaluated. Most mares and foals should have a period of exercise restriction in a small foaling paddock/unit, although foals with severe deformities should be immediately stall rested. It can be quite amazing how quickly foals with severe deformities can improve with stall rest, as well as how quickly they can deteriorate with excessive exercise. There is a balance between paddock exercise and stall rest to encourage the correction of deformities. A short period of stall rest early in life is not detrimental to the foal’s development, although prolonged stall rest can be detrimental. There is no doubt prolonged stall rest can lead to the development of other orthopaedic (eg OCD) or medical - 95 -
problems (eg respiratory disease) and a balance needs to be established between necessary stall rest and paddock exercise. It can be difficult to determine when a foalâ€™s conformation has improved sufficiently to allow movement to a paddock. In general terms, if the deformity has improved significantly then movement to the paddock should be allowed. To confuse the issue, deformities that are not improving can sometimes benefit from paddock exercise. Determining the most appropriate treatment can only be done correctly with regular assessments of a foalâ€™s conformation. Sometimes it is necessary to challenge a foal with short periods of exercise in small paddock and assess the change in conformation. I think you should always being trying to encourage some form of paddock exercise, providing it is not obviously detrimental to the foalâ€™s viability. Periods of stall rest are also beneficial later in life when some types of angular limb deformities occur. If stall rest is thought necessary, short periods of time (1-2 hours) in a small paddock during this time should be given if possible. This helps to prevent the development of other orthopaedic problems as well as stereotype behaviour (eg windsucking, weaving etc). Stall rest if often advised after surgery, although we have been developing surgical techniques in recent years that require less stall rest in an attempt to care for the horse as whole, rather than just fixing one problem. Most farms in the Hunter Valley have paddocks of varying size to allow varying levels of exercise and this is ideal. As foals are moved from periods of stall rest they should be gradually reintroduced into larger and larger paddocks. This helps to prevent over-exercise and injuries such as fractured sesamoids. It is also advisable to place all foals with conformational faults in the same paddock for ease of constant surveillance and treatment. 2. Farriery Regular trimming and corrective farriery is paramount to the development of a foals limbs and feet. The farriery has the enviable ability to examine conformation on a regular basis and is often relied upon to identify conformational faults well before the veterinarian. A good relationship between a farms farrier and veterinarian is very important and this is recognised by both parties. The specific details of appropriate farriery will be discussed by Mr M Neville.
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3. Surgery There are two commonly performed surgical procedures for the treatment of angular limb deformities. Periosteal elevation or “strips” are a relatively simple procedure, often undertaken on the farm. A strip involves lifting a section of periosteum (a skin-like lining of the bone) from the bone next to the growth plate on the short side of the limb. A foal with a valgus deviation would have surgery performed on the outside of the limb, and a foal with a varus deviation would have surgery performed on the inside of the limb. Surgery is undertaken to encourage growth at the growth plate on the same side as the surgery, thereby improving the deviation. This surgery is thought to work by causing inflammation at the growth plate, and by releasing a tethering effect of the tight periosteum. The periosteum heals with time, both reducing the inflammation and restoring the tethering effect. It is generally thought a strip will have an effect for up to four weeks. We know that foals have their fastest growth at birth (which slows with age) and that strips work by speeding growth, therefore, strips will have more potential for effect if done early in life. There is some controversy whether strips are needed or actually work. This is brought about by the fact that many foals will self correct with time. Most surgeons will have advised a strip be performed, which was not undertaken for various reasons, and the deviation improved anyway. Unfortunately we do not have a crystal ball and know which deviations will definitely self -resolve with time. There is a window of opportunity to perform this surgery and a decision must often be made between conservative treatment with time, and stripping. I have no doubt some foals are stripped which would have self resolved. However, but by the time you know that conservative treatment has failed to resolve the deviation, the opportunity for a strip to work has been lost and either a permanent deviation will result or more invasive surgery is required. There is one veterinary research article that questions the effectiveness of this procedure. The proponents of stripping question the timing that surgery was performed in this article and the critics of stripping suggest this article proves stripping does not work. In my opinion stripping can be an effective method to correct deviations, but it must be done at an appropriate age and on certain types of deviations. Stripping has become less popular with the introduction of better methods for “bridging” (another surgical procedure that will be discussed next) which cause fewer cosmetic blemishes.
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I rarely perform strips at the knee in foals with valgus deviations, not for the reason it does not work, but because many of these deviations resolve with time. The growth plate at the knee is “open” until 18 month of age and there is plenty of time to allow conservative treatment, and for “bridging” later in life if the deviation persists. However, there a number a number of good reasons why strips are done at the level of knee and these include; a more rapid correction of a deviation to prevent the need for confinement, the treatment of varus deviations at the knee which are harder to correct, and the correction of the knee deviations sooner so that other compensatory deviations do not occur lower in the limb. It has been my experience that foals with moderate knee valgus deviations that do not improve quickly have a higher risk of developing varus deviations at the fetlock, which are definitely harder to resolve considering the age by which these deviations occur. If a strip is to be performed at the knee the ideal time for the procedure is at 4-6 weeks of age. This allows time for self-correction, but there is still plenty of growth potential at 6 weeks to give the procedure a good chance of working. A strip on a foal with a severe deviation (i.e. greater than 15 degrees of deviation) is usually unrewarding and bridging is usually needed. I commonly perform strips for fetlock deviations, with varus deviations being the most common. I very rarely see valgus deviations at the fetlock and will always prove the deviation is real before doing surgery by taking a radiograph and measuring the angle of the bones. Most foals that present to me with valgus fetlock deviations actually have an outward rotational deviation, which will not improve with a strip. Many foals with fetlock varus deviations are also offset at the knee and this conformation makes it more likely the fetlock deviation with persist and not respond to conservative stall rest. I prefer to strip the entire inside aspect of the ca non for fetlock deviations as I find it more effective. I will commonly recommend hoof wall or shoe extensions at the time of surgery as a better result can be achieved. I rarely perform strips at the level of the hock for treatment of varus or valgus devi ation as I have been very disappointed with the results. The other type of surgery commonly performed is transphyseal bridging (“bridging”). This involves placing implants into the bone at the level of the growth plate to stop growth on one side of the limb, while allowing the other side to continue growing and correcting the deviation. Once the deviation has resolved the implants are removed at a second surgery, allowing both sides to - 98 -
continue growing. Bridge surgery has been performed for many years, initially using special staples or screws and wires (see Figure 1) but a newer technique using one single screw (see Figure 6) placed across the growth plate has become a lot more popular in recent times. This technique provides a much better cosmetic result, fewer complications and less after-care is needed. Initially the single screws were made from stainless steel, although the Scone Equine Hospital has pioneered the use of absorbable screws for this surgery.
Figure 6 A single stainless steel screw, 3.5 mm in diameter, has been placed across the growth plate at the level of the lower canon for treatment of a varus deviation at the fetlock. This is commonly caused a â€œSingle screw bridgeâ€?
Bridging is highly effective surgery providing it is done prior to the growth plate closing at the site of the deviation. There is no controversy as to its effectiveness. However, compared to strip surgery, bridging is technically a lot more difficult, must be done in a sterile theatre, requires more after-care and has the potential for more serious complications. For this reason, conservative treatment, farriery and strips are often undertaken before bridging is considered. Bridging can be undertaken after these techniques are tried because there is a much large window of opportunity to perform the surgery. From previous experience on over 300 foals we know that a grade 2 varus deviation at the fetlock can still be corrected at 3 months of age. There is no other technique that could provide this result. In the last few years we have become a lot less aggressive with all other forms of treatment and allowed Mother Nature a chance of correcting the deviations. If she is not successful we can still bridge the foal at a later stage. I am now recommending that foals with persistent fetlock varus deviations should be evaluated for bridging at 10-12 weeks of age. I particularly like this approach - 99 -
as it avoids prolonged stall confinement early in life when these foals should be running in paddocks to encourage normal development, and excessive farriery that may result in permanent foot deformities. Bridge surgery can also be performed at the level of the knee and hock, and is highly effective. You can still expect to see a significant improvement in a knee deviation at 12 months of age and a hock at 6 months of age. As mentioned earlier the SEH has pioneered the use of absorbable screws for bridges at the level of the fetlock. We undertook a research project on 6 foals with varus deviations at the fetlock and demonstrated with radiographs that the screws were highly effective. The advantage with these screws is that they do not have to be removed, avoiding further surgery, with its risks, costs and after-care. One potential concern with this surgery on horses that are to be sold as yearling is that the screws takes-1-3 years to be absorbed, and they will be seen on repository radiographs (see Figure 7). The timing of implantation of these screws is important as it must be done so that the growth plate is closed at the same time as the deviation has resolved.
Figure 7 This foal has an absorbable screw placed at the level of the lower canon. The screw cannot be seen but a hole in the bone can be seen at the same position as the screw in Figure 6. The growth plate has now closed and cannot be seen. The screw will slowly absorb over 1-3 years and this hole should fill-in with bone.
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Conclusions To put it in simplistic terms: foal conformational leads to yearling conformation which ultimately leads to success in the sale ring and racing soundness. It is one thing we can influence during the development of young horses and visually see a benefit. The methods of treatments continue to evolve and constant updating of your knowledge and skills is vital to the horse, and for your future worth in this industry. I hope this article and lecture helps to achieve some of these goals.
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Laparoscopy and the application of Prostaglandin to the Oviduct to treat blocked Oviducts and Infertility in Broodmares Laparoscopy is a surgical technique where a long camera is placed into the horse’s abdomen to view the internal organs and structures (Figure 1). It is a similar process to arthroscopy where a smaller camera is used to view a horse’s joint. The advantages of laparoscopy over the more well known technique of “open” surgery, such as colic surgery, is that the procedure can be done standing, it causes a lot less trauma, has fewer complications and structures can be seen and treated which are not possible with traditional “open” surgical techniques. Laparoscopy can be used to perform a number of procedures, such as rig castration, ovary removal, assessment and treatment of chronic colic, kidney removal etc etc. A technique relevant to the broodmare has been undertaken in recent years to treat infertility due to blocked oviducts. This has been a very exciting development in our management of infertility and I wanted to make you aware of this procedure and the results we have achieved at the SEH in the last 2 years. Figure 1: This is a photo of a mare having laparoscopic surgery. The mare is sedated and standing is a set of specially designed stocks, which allow easy surgical manipulation and also rapid disassembly. The mare’s rump is to the left of me, and a large sterile drape is covering her back. There is a hole in the drape to expose the flank. The laparoscopic camera is being held by my assistant, and I am manipulating the ovary with grasping forceps. The image from the camera is visible on the computer screen on the opposite side of the horse.
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The oviduct is a narrow tube that connects the ovary to the uterus. Following ovula tion and the release of an egg from the ovary it travels to the oviduct where it is fertilised by a sperm. The developing embryo remains in the oviduct for about 5 days before it is released into the uterus. Temporary blockage of the oviduct, preventing passage of the embryo into the uterus is a recognised condition in mares and caused by an accumulation of debris from previous ovulations or pregnancies. The oviduct cannot be easily visualised during rectal ultrasound examinations and the diagnosis of blocked oviducts is made when other causes of infertility, such as endometritis, abnormal ovulation or stallion infertility are ruled out. There have been attempts to establish a more accurate way to diagnose this condition, without the need for laparoscopy, but they have been unsuccessful. We know from previous studies that prostaglandin (PG) will cause active transport and expulsion of an embryo from the oviduct and it was postulated that if PG were “painted” onto the oviduct it may flush out any blockages and restore the normal patency of the oviduct. The first published work on this procedure was from England where 14 horses were treated and very exciting results were achieved in mares that had failed to conceive following many coverings and stud seasons. The procedure is done 4 days following ovulation. At this stage she is hopefully carrying a developing embryo that is residing in the oviduct. The procedure is done with the mare standing, sedated and restrained in a set of specially designed stocks. The flanks are clipped, surgically prepared and a large drape placed over the horse. Following the injection of local anaesthetic, two or three hollow trocars are placed into the horse’s abdomen from the left flank. One is used for a long camera, one for forceps to allow manipulation of the ovary, and the other for a long tube to allow the “drizzling” of a PG gel onto the oviduct. Once the camera is positioned into the horse abdomen carbon dioxide is used to inflate the abdomen so the internal structures can be see n. The ovary, oviduct and uterus can be readily seen. Any dilation of the oviduct is obvious and the cannula can be positioned directly onto the oviduct and PG gel drizzled onto the entire duct (Figure 2). The procedure is then repeated from the right flank. The procedure is done at 4 days after ovulation to coincide with the natural timing for movement of the embryo into the uterus. Although serious complications are possible during the procedure, it is well tolerated and the mare is normally allowed into a paddock on the day after surgery. Some pre-operative and postoperative procedures or treatment are needed, but most horses return to the stud farm the day after surgery. - 103 -
Figure 2: This is an image of an oviduct during the procedure. The ovary is to the right of the image and uterus to the left. The oviduct is pointed to by the black arrows and a metal cannula can be seen â€œdrizzlingâ€? a gel onto the duct. This is an obviously dilated oviduct.
We undertook this procedure on 10 mares in 2009 and 22 mares in 2010. The only major complication encountered was in one mare than developed acute diarrhoea, although this resolved within 5 days and the mare still conceived a pregnancy on the same cycle as the surgery. It is common for some mild post-operative pain and a reduced appetite for 24 hours, although this is easily treated with appropriate medication. The results from 2009 are listed on the following page:
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2009 Stud Season Mare Age
Number of years barren
Pregnant 3rd cycle
Pregnant 2nd cycle
Pregnant 1st cycle
Pregnant 2nd cycle
Failed to conceive
Served on two cycles
Pregnant on 1st cycle
Pregnant on 2nd cycle
Lost preg between 18 and 30 days
Pregnant on 3rd cycle
Pregnant on 1st cycle
Failed to conceive
Served on three cycles
An 80% 15 day conception rate was achieved, although one mare lost her pregnancy between an early and mid-scan. Of the ten mares, 30% were pregnant on the same cycle as surgery, 30% on the second cycle and 20% on the third cycle following surgery. This year we assessed the conception rate during the 2010 season of the 8 mares that had conceived a pregnancy in 2009 and this gave us confidence the procedure lasts for at least 2 years. This reduces the relative cost to the mare owner and the risks to the mare from having to undertake surgical procedures on an annual basis. We are very excited to have this procedure in our arsenal of weapons to treat infertility. Having undertaken the surgery on 32 mares, and 64 ovaries, we can confidently offer this procedure by experienced surgeons, thereby reducing possible complications and allowing an experienced opinion.
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Foal farriery & notes on laminitis assessment and treatment Lecture Six MICHAEL (‘SPOOK’) NEVILLE , Farrier
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Foal Limb Correction There are 2 natural causes which make it important for us to monitor foal limbs in the early stages of their young development. Foals are born with a very soft, pliable hoof, not much harder than jelly! This hoof hardens in time relative to conditions. Foals that are stabled or in irrigated yards, take longer for the hoof to harden than those in harder yards or paddocks.This hoof is generally long and is vulnerable to uneven wear or breaking away as it hardens, due to conditions and conformation. Foals are also born with very little muscle tone. They are very flexible and susceptible to change at an early age. This muscle tone develops rapidly, so it is very important to aim his correction along with muscle development. It is easier to correct a foal limb while the muscles and joints are developing, especially when correcting upright or flaccid foals. Therefore it is important to look at foals at: ď‚ˇ
7-10 days of age, to ensure that the soft hoof is worn evenly, to ensure minimal pressure on growth plates. As well as being able to grade the foals limbs so that the grades can be compared at the next trim.
It is then important to have a re examine date that is adhered to. In most cases, 10-14 days is sufficient, but worse cases in 7-10 days
a second assessment at 20-24 days of age, is important to ensure the grade of the limb is correcting not worsening, as the best window for lower limb correction, especiall y using periostal elevations is at 3-5 weeks with most normal developing foals.
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Angular Limb Deformities in Foals Angular limb deformities (ALDs) are becoming more commonly observed in foals of all breeds for a number of reasons including over-nutrition of mares, intra-uterine malposition, ingestion of toxins by pregnant mares, and other metabolic imbalances such as defective ossification. The treatment of such foals has become more critical, especially for breeds of foals intended for high level competition. The level of treatment can range from regular therapeutic trimming, to a number of other methods, including extensions and surgery, (being mindful of the goals of the client) in considering if the foal is to become a sale prospect, a pleasure riding horse, or an athlete. Remembering that even sale prospects should have a balance between making a sale, and the horse continuing on to become a performance athlete.
1. Initial Observation It is recommended to have an initial observation of all foals between 7 - 10 days of age. In many cases foals born with mild (G1) deviations can be corrected at this age with a lesser effort, due partly to improving muscle tone and strengthening ossification. It is also highly important as the new hoof is still in a pliable state. The hoof hardens considerably over several days (depending on conditions) and can harden into an imbalanced or broken away state, causing stress on growth plates etc. You should try to envision the foalâ€™s growth development. This can take some experience, but is a very important step towards an end result. Firstly, take notice of the conformation and characteristics of the dam (mother) and also of any genetic traits of the sire.
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Consideration should then be given to muscle, height, and the environment, and lastly, whether the foal was premature or not. It is always very important to take note of the foaling date (eg: tag on the mare). 2.
It is very important to closely monitor the foalâ€™s progress right from the first consult through to yearling stage if possible. Keeping a consistent grading technique is vital for further consultations. Good grading can assist in deciding if the ALD is improving or not, which can in turn indicate whether or not to be more aggressive with further treatment. It is also very important to synchronise your grading system to others you work with (i.e. vet, farrier, stud groom, owner etc.) in order to liaise competently together. A grading system from 1 to 4 is widely used: Grade 1
being a mild deviation (etc) which is noticeable
an obvious deviation which is easily recognised and warrants extra treatment.
a major deviation requiring immediate attention plus stall rest in most cases.
being a disaster case (weigh up options)
Dr Angus Adkinâ€™s Grading System example. +1V = Grade 1 valgus knee (+ means valgus) -1V = Grade 1 varus fetlock (- means varus)
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Common ALD Conditions in Foals Offset or Benched Knees and Varus (Deviating in) Fetlocks It is becoming more common in most breeds for foals to be born with an offset knee and varus fetlock conformation. These cases require constant monitoring using a grading system as the condition worsens with most foals, due to weight gain and muscle development through to yearling stage. Even at 7 -10 days, foals with o/s dev in will have excess medial toe growth due to load gain on the lateral side (especially the heel) which can cause uneven growth plate load (compression on the medial side) creating a worsening effect.
cases can be corrected successfully with balanced trimming on a regular basis, using grading to ensure progress.
cases at 7 â€“ 10 days should be trimmed down to level and re-examined in 7 days, depending on the result whether to push a further 7 days if improved, or a decision made for lateral extension and/or periosteal elevation (strip).
cases generally require stall rest â€“ knee is often bowed as well. A lateral Dalric extension (or equivalent) can be taped on for support even earlier than 7 days and glued on afterwards if no improvement.
Most will require medial p.e. and possibly cannon or medial knee p.e. with extensions. Some cases can also have flexor tendon misalignment, medially. These cases can be difficult and require regulated exercise.
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It is important to note that fetlock growth plate (distal cannon) ossifies at 6 â€“ 8 weeks, so p.e. results are gained from 3 â€“ 5 weeks.
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Narrow Chest Base Wide, Rotate in with Varus fetlock Quite common in lighter breeds (t/bred, light performance horses) and also in some foals born early or first foalings. Most of these foals can be difficult to re-align, but can carry this confirmation into high level competition as most rotate in (heel out) deformities commonly land flat during flight, although will have a wing out (paddling) action. Most will have an off-set knee with a slight valgus. I have noted that over correction of varus fetlock (with strip or bridge) can aggravate valgus knee as an early yearling. Dalric extensions do not have the normal effect due to even load on landing flat. Small Equithane extensions with weekly monitoring can be effective, or strips (p.e.) with no extension. We use very few bridges on these cases.
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Rotate Out Another of the more common limb deformities - also one of the hardest to correct. It is important to note whether the foal has a narrow chest and whether the foal has a varus fetlock or hangs in, in flight – as rotate-out horses will always wing in, in flight. If the foal has a varus fetlock as well, the flight will be over-emphasised and can cause brushing during performance. A rotation can be detected during assessment by landing on the lateral heel first. Patience is the key to rotate-out deformities – being aware of varus fetlock as there is limited time to correct fetlocks. Chest muscle development helps to correct. Rotate out cases with off-set knees will often bow in flight. The bowing action should decrease as chest development increases.
Grade 1 – 2 Level trim at 7 – 10 days. RX 10 – 14 days. Level trim, again dressing medial toe (if hang in)
Grade 3 If there is no indication of varus fetlocks, stall rest with shallow bedding, and medial Dalrics taped on or glued with close monitoring of fetlocks. Never use medial Equithane, as it tends to pull hoof capsule in rapidly. Patience is the key. Be aware of possible pain related issues and chest muscle tears. Chiropractic – even low grade hoof pain can cause rotational deformity (watch for dragging in flight). - 113 -
As long weaners or yearlings, exercise to develop chest muscles can help (aquatread, ponying).Lunging in heavy conditions is not recommended as interference in flight can occur especially when tiring.
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Forward Knees – Down in Pasterns - Bowing in Flight Each year I have noted 2 – 3 foals in this condition – generally heavy shouldered foals. If there are no major deviational faults, possibly treat with Cu-algesic or bute (low doses). Restrict exercise, slow down growth rate and look for early weaning if lacking improvement.
Windswept Foals born with a windswept conformation (front limbs aiming left/ hind limbs aiming right), often have a slight curvature of the spine. These foals will often respond more readily to treatment as muscle tone improves and spinal column straightens. More attention to treatment of the varus affected limbs with extensions to support load forces generally improves curvature.
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Upright (Ballerina syndrome) â€“Contracted Tendons Many foals are born with or acquire many variables of tendon contraction â€“ in many cases due to growth spurts (tendons not growing at same rate as bones). Foals born with deep flexor contractions (DFC) should be stall rested immediately. Support or 3 day casts are recommended in most severe cases of DFC. Foals heel(s) will be off the ground, resulting in excessive load on toe area, which can cause sole compression or bruising to the extent of small fractures of (distal) P3. Raised heel (wedged) Dalrics can be taped on and monitored daily, with use of oxytetracycline (oxytet) and/or Cu-algesic -dosage recommended by veterinarian. Do not give oxytet before foal is 24 hours old. Ulcergard is also recommended with use of bute or Cu-algesic
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If a wedged Dalric is glued, the wedge can be rasped down into a rocker shape as the foal progresses. The wedges are important tools in these situations, as they help distribute weight evenly (heel – toe), easing toe compression and also aiding in “resting” DDF, allowing the tendon to stretch (lengthen) when the heel is adjusted. If wedges are used in older foals (up to yearlings) the height of the wedge should be twice the angle (or height of heel to ground) after de-rotation when the affected leg is half a step behind normal position. The 4-point or rocker trim is recommended thereafter. In a lot of tendon contracture cases, mechanical forces can cause bowing or toeing in conformation. Lateral Dalrics with wedges can be used with the wedges alternated (on – off) as required or lateral Dalrics used in soft, deep bedding. In severe cases where little response to treatment results in a club, surgery can be used. Either check ligament cut, or deep flexor above attachments of check (refer Dr Redden) . De-rotation of P3 plus slight toe extension and raised heel putty can be applied, shortening the heel over 24 hours. Some post-surgery scarring is to be expected. One of the main goals is to maintain blood flow to circumflex arteries to promote sole growth and keep hoof quality by keeping even load pressures similar to laminitic cases. Knuckling forward of the fetlock is generally an indication of the contracture of the superficial flexor tendon, which can be very difficult to treat mechanically. Stall rest and light exercise is recommended. Also, can be pain related, so use of Cu-algesic is an option.
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Valgus Knee (Carpus) or Medial Deviation The valgus knee conformation is very common in young foals – especially weak or premature foals. The valgus deformity can be caused by poor ossification of the carpal bones (carpal bones can appear rounded with spaces between, indicating a lack of mineralized cartilage). Early diagnosis, restricted exercise and treatment can prevent further compression to carpal bones and compression to lateral side of the growth plate. It is very important when evaluating valgus knees (especially bi-lateral) to note whether the foal has a narrow chest, as most will improve as the chest develops, load forces shift and muscle tone develops. Grade 1 - valgus knee cases are generally self-corrected – a level trim, RX 10 – 14 days. Grade 2 - cases require a level trim at 7 – 10 days, but need constant monitoring and restricted exercise. It is also important to watch for hang in (wing in, in flight), which is a compensation for load forces Grade 3 - cases need stall rest. Often the foal will need figure-8 support wraps and/or medial Dalrics taped on – closely monitored to ensure no over-correction of fetlock. We have had many cases of Grade 3 valgus where over-correction of the fetlock was apparent and lateral p.e. was necessary. Medial fetlock p.e. was performed at the same time. Growth plate above the knee ossifies at 8 – 12 weeks – therefore, allow time for other treatments before performing a p.e., as over-correction can be common. Also, note pinching or shortening of lateral physys (has a scalloped look) this can be an indication that a p.e. is warranted at this stage. - 119 -
Flaccid tendons Many foals are born with flaccid tendons (down in pastern) more common in hind limbs. Premature foals are especially prone. Stall rest is recommended and the application a couch heel made of vetwrap and support bandages for the first 24 hours. Dalric heel extensions can be taped on for the first 2 â€“ 5 days. After noticing a strengthening of muscle tone, heel extension can be alternated (on â€“ off) in 24 hour intervals to allow strengthening to continue. (If heels are left on they become reliant). It is important to trim affected feet flat from toe to heel (sometimes lowering the heel) to alleviate a fulcrum (point of balance) to rock back behind. By pushing the point of balance back it promotes a rock forward to the toe. In severe (Grade 3) cases, a sublaxation of pastern joints can occur. Restricted exercise is essential, and a rocker shoe can be applied in older foals after muscle tone improves. Often flaccid tendons can be associated with bowed hock and/or varus fetlock. A Dalric extension shoe - modified to include heel/lateral support by use of an aluminium plate riveted on (see sickle hocks).
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Hind Limb Varus Deformities There are a remarkable percentage of newborn foals with varus fetlocks. Noticeably in Australian thoroughbreds, there is a higher percentage in near hinds (left rear), possibly due to intra-uterine malposition. Bowing hocks can also be very common. Grade 1 cases can be easily corrected by level trim at 7 – 10 days. RX 10 days - monitor. Grade 2 cases require trim at 7 days. RX 7 - 10 days for possible lateral extension (use Dalric if hock is bowed). Grade 3 cases require stall rest and lateral Dalric taped on as early as possible. RX 7 days (possibly glue on Dalrics will be needed). It is noted that p.e. on hind limbs do not respond as well as fore limbs, therefore more emphasis is needed on mechanics.
Sickle Hocks (Curved hocks) Sickle or curved hocks can be associated with flaccid hind tendons and can be the result of premature foaling. Most require restricted exercise and should be monitored weekly for signs of crushed or collapsed tarsal bones. An early indication of crushed tarsal bones can be a “bunny hop” action when breaking into a trot or canter. Hocks should then be radiographed to confirm. Hocks can be treated with minimal Bute or Cu-algesic (with Ulcergard) with complete stall rest with RX -14 reassessment. - 121 -
Long Pointy Hind Toes He untrimmed foal, even at 10 â€“ 12 days, can produce a long pointy toe. Many of which develop a deep stress bruise at the centre of the toe area, due to the stress on the laminae. Often these bruises can develop into an abcess (infection) which can travel up the laminae towards the coronary band. These foals should be trimmed in a 4-point fashion or squared off to relieve laminae stress, and monitored for infection. All infections (abcesses) should be poulticed in a fashion to draw infections to the distal hoof â€“ not encouraged to break out at the coronary band, which can leave a scarring or weakness in the laminae, which in turn can possibly lead to problems during performance years such as toe cracks.
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Applying Dalric Extensions Dalric extensions are a great aide in the treatment of many (ALDs). They can be used medially or laterally depending on whether the deformity is valgus or varus. The main aim of the Dalric Extension is to support the load forces of affected leg and to provide support for stressed sesamoids and carpal or tarsal bones as they continue to ossify. They also prevent breaking away of hoof wall which is likely due to weight bearing forces. I prefer to only use Dalric Extensions on foals up to 14 days as they support the hoof completely medial/lateral and should only be taped on up to 5-7 days. After 14 days a decision can be made whether to utilise Equithane Extensions or continue with Dalrics. In most cases where a knee or hock is bowing Dalric use should be extended. In the case of a foal rotating in the Dalric has less mechanics (see notes) therefore other treatment is necessary. The Dalric Extension has an adjustable wall which should e fitted firm but not tight, trying to allow some expansion toward the heel area. The heel area of the Dalric shoe should be modified as to not affect the coronary band. The shoe can then be either taped on (for short periods on young foals) or glued on with either Dalric Glue (provided) or with Equithane. With the aid of Elastoplast to hold shoe in place until glue sets. When a Dalric is taped on one wrap around the hoof capsule then continued around the Dalric helps prevent shoe twisting on the hoof. It is recommended in young foals (up to 30 days) that the Dalric be removed before 7 days, after that they should be removed before 10-12 days. A close daily monitor of Dalrics several days after application is essential. Watching for signs of over correction (if used medially) also in severe cases a bulging of the coronary band can occur which is an actual expansion of the coronary band not a contraction of the hoof, which many people are lead to believe. If this occurs beware of slight vertical cracks below coronary band, which left unnoticed can become infected and be very painful. If this occurs remove shoe immediately and reassess for reapplication or possible Equithane. I have noted some cases where lateral extensions are used on hind limbs with bowed hocks where there is a lot of hock action, that the shoe can grip on ground surface which can cause an aggravation of the coronary band, resulting in a horizontal crack. Softer bedding is recommended for these applications. Most Dalrics have best results in softer bedding where available.
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Applying Equithane Extensions Equithane extensions are predominately utilised laterally in cases of varus fetlock deformities and rotated in deformities and are used often in conjunction with periostal elevation surgeries. It is not recommended for use on foals less than 14 days old or until hoof structure is capable of supporting an extension. Equithane should not be used on foals with any hoof wall weaknesses or cracks, etc, as the high temperature during setting time can result in a scorching of the laminate, causing infections. Also try to avoid applying Equithane to young foals in very hot conditions as rapid setting of the Equithane cases extreme heat and may cause laminate aggravation. Try to avoid foals being subject to hard surface conditions, as there have been a number of cases of lameness associated with foals galloping on hard conditions possibly causing slight P3 fractures. The amount of extension required depends on the severity of the deviation being aware of cases
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where there is a valgus knee involved with varus fetlocks, especially in some narrow chest base wide foals (see notes).
Application of Equithane extensions and the benefits of their use Equithane extensions are predominately used in cases of varus fetlock deformities and are used often in conjunction with periostal elevation surgeries In the case of offset or benched knees, with varus fetlocks, the effects of the load forces of the affected limbs, play a major part in the correction process of the limb. In most general cases of offset knees with varus fetlocks that are untreated, the weight bearing load forces are down on the lateral side of the leg, causing excessive wear and compression on the lateral hoof wall, and in turn allowing medial growth of the hoof, causing an upward load force on the medial aspect of the leg, which creates a compression of the growth plates above the knee and fetlock. Left untreated, the compromising of the medial growth plates, can cause prolonged damage and pain related issues such as epiphysitis etc. that can lessen the chance of creating an early athlete or even a sale yearling. In grade 1 cases, regular trimming from 7-10 days can be sufficient treatment. In grade 2 or 3 or worsening grades, the effects of reversing the load forces are very beneficial, especially in conjunction with periostal elevation surgeries (strips). Which is the lifting of the outer layer of the bone, releasing the pressure on the growth plate, and by lowering the hoof on the medial side and applying a lateral extension, changes the load force from down on the lateral side and up on the medial side, to up on the lateral side and down on the medial side. Thus helping to straighten the leg and reducing compression of the medial growth plate, often easing pain related issues and reducing epiphysitis in later months, hopefully creating a more saleable yearling or an earlier athlete. Equithane extensions are not recommended on foals less than 14 days old or until the hoof structure is capable of supporting an extension, and should not be used on foals with any hoof wall weaknesses or cracks etc, as the high temperature during setting time can result in a - 125 -
scorching of the laminae, causing infections. Also try to avoid applying equithane to young foals in very hot conditions as rapid setting of equithane causes extreme heat and may cause laminae aggravation. Try to avoid foals being subject to hard surface conditions, as there is a higher chance of possible lameness issues including slight P3 fractures. The amount of extension required depends on the severity of the deviation, being aware of cases where there is a valgus knee involved with varus fetlocks, especially in some narrow chest, base wide foals. (see notes). It is not recommended to raise or wedge the extension on the hoof, but to make it a level extension of the hoof plane.
Club Feet Club feet are a common deformity among all horse breeds. Predominately worse in one foot than the other. Club feet can be genetic, but can often be acquired due to a number of reasons including, growth spurts, injuries or neglect. I find it very helpful to grade club feet, so as to guage the progress of the foot visually, as well as radiographically. Therefore being able to give an assessment as to whether a cha nge of treatment is necessary! It is fairly universal to grade clubs from 1-4. Grade 1. A grade 1 club is a foot that has an obvious difference in hoof angle and higher heel growth than the other foot. These clubs are generally managed easily by restricting growth and mild therapeutic trimming. Grade 2. A grade 2 club is significantly steeper in hoof angle, and has signs of growth rings that are narrower at the toe and wider at the heel. These clubs can still be managed by restricting growth, as well as therapeutic trimming-shoeing and possibly the use of anti inflammatories or pain relief drugs administered by a veterinarian, if diagnosed as being pain related. Grade 3. A grade 3 club is a foot that has all of the characteristics of a grade2, but has a dish in the hoof wall at the toe and generally has thin walls through the quarters. Often the heel of the affected foot, (when placed half a step behind the other) has a gap between the heel and the ground. This leg can also be slightly back at the knee and a broken hoof-pastern axis. These clubs often need surgery as well as therapeutic farriery
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Grade 4. Grade 4 clubs are generally disaster cases, with all characteristics of gra de 3 only noticeably worse. They have a major dish and often have a hoof wall angle of 90 degrees below the coronary band. These clubs are very difficult to maintain without the aid of surgery. Radiographs are a very useful aid in treatment of all clubs and recommend that lateral shots be taken of all grade3 and 4 clubs, or any hoof that has a worsening grade, before a prognosis is reached. There is very valuable information to be obtained from lateral radiographs of all feet, that is useful to both vet and farrier. The common hoof parameters that can be seen on true lateral shots, give a good guide to the general health of the hoof and can be compared to the range of normal for a horse of similar age, breed, etc. It is important to note that when comparing parameters with previous radiographs, that the same technique be used for both shots to get an accurate reading! I find for lateral shots, that the xray beam should be placed about 1.5cm above hoof surface for best result. Some of the most important hoof parameters are. Sole depth (S.D.) - The measurement between the tip of the pedal bone, vertically to the ground surface. Palmar angle (P.A.) to the hoof - The measurement of the angle between the pedal bone and the hoof surface. Palmar angle (P.A.) to the ground - The measurement of the angle of pedal bone and the ground surface. Horn-Laminae Zone (H.L.) - the distances between the pedal bone and dorsal hoof wall, at 2 points. Just below the extensor process and at apex of P3 Digital Breakover (D.B.) - the measurement from the point directly below the apex of P3 forward to the point where the hoof or shoe does not make contact with the ground. Some other pathology to look for with club feet radiographs are , bone alignment through P1 to P3, the apex of P3 beginning to lip or curl up and small fractures around the apex of P3 . these can be signs of chronic clubs.
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Wound Management Lecture Seven DR TROY BUTT, Diplomate ACVS
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Types of Wounds 1.Lacerations: a. Most common type of wound b. Tissues with good blood supply heal the best i.
Lacerations over muscles
c. Tissues with poor blood supply do not heal as well i.
Lacerations below the knee or hock
2.Puncture wounds a. DANGEROUS b. Often become infected because hole seals over and bacteria/foreign material are
sealed in c. One of the most common causes of joint infections
Wound Healing 1.Vascular constriction a. Most bleeding will stop on its own b. Arteries on legs will stop bleeding with a pressure bandage c. A small volume of blood will look like a lot! A horse can loos e 50 % of its blood
volume and survive! i.
500 kg horse can loose 20 litres of blood
2.Inflammation a. Creamy exudate is normal in open wounds b. White blood cells are removing dead tissue c. There will always be SOME drainage from an open wound - 129 -
3.Repair a. Wound fills with GRANULATION TISSUE i.
Made up of blood vessels and connective tissue
Too much is called â€œProud fleshâ€?
iii. Generally, proud flesh only develops BELOW the knees and hocks. iv. Proud flesh formation can be avoided by bandaging. b. Edges of skin appear white i.
ii. Normal healing
4.Contraction a. Skin closes over proud flesh b. Epithelial tissue is NOT normal skin: It does not have hair follicles or pigment and is
Emergency Wound Management 1. Stop bleeding if possible a. Limbs: Pressure bandage b. Neck: Compress with towel and tape 2. If not bleeding, clean wound a. If wound is fresh, keep as clean as possible b. If wound is dirty, hose with water i.
Sometimes hosing can start the bleeding again!
3. Call for assistance
Wound Care 1.Lacerations on head a. Usually heal without complications b. Minimal movement, so usually closed with sutures - 130 -
c. If wound cannot be sutured due to loss of skin, these wounds will heal as an OPEN
WOUND. They will repair and contract rapidly with good cosmetics. 2.Lacerations over muscular areas (ie above knees and hocks) a. Often are not sutured due to high mobility (ie neck, shoulder) b. Will heal very well as an OPEN WOUND because good blood supply from the
muscles underneath 3.Lacerations below knees and hocks a. More problematic i.
Blood supply is not as good
ii. Are often sutured to cover bones, joints, and tendons. iii. Bandaging is essential 4.Treatments a. Antibiotics i.
When to use 1. Wounds that do NOT have drainage (ie sutured wounds). 2. Wounds close to joints
ii. When NOT to use 1. OPEN WOUNDS WITH GOOD DRAINAGE AND NO JOINT
INVOLVEMENT DO NOT REQUIRE ANTIBIOTICS 2. DIRTY WOUNDS WILL STILL BECOME INFECTED WITH
ANTIBIOTICS iii. Broad spectrum 1. Penicillin and Gentam 2. Sulprim b. Topicals i.
ii. Silvazine iii. Prednoderm
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c. Bandaging i.
EXTREMELY IMPORTANT FOR LOWER LIMB WOUNDS
ii. Maximizes cosmetics iii. Prevents proud flesh iv. Speeds healing
Wound Complications 1. Infections a. Occur in contaminated wounds (dirt, hair, manure) b. Antibiotics are NOT effective if there is dirt in the wound 2. Suture breakdown a. Will usually occur before day 10 i.
ii. Wounds over areas with high mobility iii. Wounds with poor blood supply b. Results in further loss of skin because skin dies when sutures pull through 3. Scarring a. Often worse in a sutured wound than a wound left to heal on its own b. Large wounds often heal with epithelial tissue i.
ii. No hair iii. No pigment
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Scoping Hores & Racetrack injuries related to conformation Lecture Eight PADDY TODHUNTER, Diplomate ACVS - 133 -
Endoscopy of the upper respiratory tract in yearling thoroughbreds Routine endoscopy of the upper respiratory tract for yearling sale purposes includes visualization and assessment of function of the upper airway structures of the larynx and pharynx primarily, as well as the nasal passages, guttural pouch openings, and the entrance to the trachea/windpipe. It is performed with a flexible fibreoptic endoscope attached to a light source and viewed directly or videoendoscope and viewed remotely via a monitor/TV (or more recently with small LCD screen conjoined to the scope). The procedure is performed in a box or preferably a crush restraint for safety and very importantly with a good handler holding and restraining the horse. Most horses tolerate the procedure reasonably well usually with extra restraint from a nose twitch or sometimes with a skin twitch or skin fold for those not keen on a nose twitch. Occasionally sedation is required but this can interfere with function of the pharynx or larynx causing relaxation of the structures and therefore inaccuracy in differentiating true abnormalities from induced abnormalities. The scope is passed through the nose via the lowerpassage (ventral nasal meatus) to the pharynx where the larynx can be visualized. Usually the first 10 cm of the passage up the nose is the part of the procedure that is least well tolerated but horses also react to the initial twitch placement sometimes violently and to exiting of the scope and removal of the twitch at the end of the procedure. So be careful and watch their eye and there front feet and anyone else in the firing line vet included! (Anatomy of pharynx and larynx- important structures to note are pharyngeal roof and walls including the palatopharyngeal arch, guttural pouch openings, soft palate and the larynx particularly the arytenoid cartilages, the lateral ventricles and vocal cords, the epiglottis and the aryeppiglottic folds. ) Once in the pharynx, the walls and roof are evaluated and the openings to the guttural pouches and the soft palate can be visualized. Primarily the structure and function of the larynx is assessed. Usually it is important to assess the structures while swallowing (stimulated with water via the scope or gentle touching of the scope against the larynx) and sometimes with nasal - 134 -
occlusion to increase respiratory effort and occasionally with a â€œslap testâ€? (a neurological/spinal reflex that involves slapping one side of the wither that causes outward movement (abduction) of the opposite side arytenoid cartilage of the larynx).
Abnormalities of the Pharynx Pharyngitis Pharyngeal lymphoid hyperplasia is reactive immune tissue in response to exposure to antigens/toxic proteins from infection (bacterial and viral) and stabling. It is the most common abnormal finding in yearlings in sale preparation. It is unlikely to affect exercise performance and therefore post sale endoscopic examination unless severe. However due to the potential of causing other local infections such as pustule formation and that it reflects underlying inflammatory disease that has been incriminated in other upper airway dysfunction such as soft palate displacement and infections of the arytenoid cartilage (arytenoid chondritis) it is often treated prior sale. Treatment includes anti-inflammatories (topical throat medication and systemic Phenylbutazone and occasionally cortisone) and antibiotics. Pharyngeal Cysts Cysts are large blister like fluid filled structures that are congenital abnormalities that occur most commonly under the epiglottis and also along the wall of the pharynx and on the soft palate. They cause exercise intolerance and respiratory noise. Treatment involves removal via external incisions into the throat (laryngotomy, pharyngotomy) or via the nose or mouth with lasers and snares. Rostral displacement of the palatopharyngeal arch This is a congenital abnormality that is usually associated with other abnormalities and causes exercise intolerance and noise. It carries a poor prognosis.
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Pharyngeal dysfunction Dorsal displacement of the soft palate Dorsal or upward displacement of the soft palate (DDSP) can be intermittent or persistent. The soft palate normally sits below the epiglottis but moves above it and flutters in the openi ng to the larynx causing noise and exercise intolerance. Many horses will displace the palate during scoping but quickly replace it to the normal position under the epiglottis with swallowing. Intermittent DDSP (IDDSP) can be difficult to accurately diagnose on resting endoscopy and often requires treadmill endoscopy. Some of these horses have ulceration at the back of the soft palate or a flaccid short epiglottis which helps diagnosis at rest. Persistent DDSP (PDDSP) is obvious at rest. It may be associated with other abnormalities such as epiglottic entrapment. Pharyngeal collapse Collapse of the roof and or walls of the pharynx are uncommon and difficult to interpret if mild degrees are found on resting endoscopy. More severe examples particularly with a history of noise and exercise intolerance may be seen at rest. Otherwise this lesion would go undiagnosed at post sale endoscopy as it would require treadmill endoscopy. There is no known treatment for neurogenic causes except for anti-inflammatories and carries a poor prognosis. If collapse is secondary to guttoral pouch disease or retropharyngeal abscesses then treatment of the primary disease with medical and /or surgical treatment may be successful. Abnormalities of the Larynx that will result in failure at post sale scoping. The larynx is the short tube between the pharynx and the trachea. It is a complicated structure that affects airflow, prevents aspiration, and enables vocalization. The following diseases will affect airflow through the larynx and cause exercise intolerance and therefore are reasons for failure of post-sale endoscopy. Laryngeal hemiplegia Normal function of the larynx involves synchronous movement of the arytenoid cartilages as they move in and out (adduct and abduct) to regulate airflow to the lungs. Incomplete abduction of one or both arytenoid cartilages (laryngeal hemiplegia) causes exercise intolerance due to reduced airflow and noise. Normally hemiplegia involves the left side cartilage. It is a result of dise ase of the left recurrent laryngeal nerve. - 136 -
Laryngeal hemiplegia is measured by several grading systems accessing movement and the degree of abduction of the cartilages. One system is as follows. Grade I is symmetric and synchronous movement with full abduction; Grade II is asynchronous movement but full symmetric abduction; Grade III is asynchronous and asymmetric movement: and Grade IV is complete paralysis. The degree of abduction is usually assessed when swallowing. Grade III is further subdivided on exercise treadmill endoscopy into IIIa with full abduction and IIIb without full abduction (and a third subset Group IIIc where the cartilage collapses). A second recognised grading system differentiates between Grade 2 and Grade 3 on whether the abduction can be obviously maintained (Grade 2ii) or not obviously maintained (Grade 3 i). Post-sale endoscopy still has trouble differentiating within this grey zone and causes much consignation prior sale and also at post sale endoscopy to interpret whether a cartilage is abducting 100% or 90% or whether abduction is maintained or not maintained in the short period following swallowing . If at rest it is reasonably conclusive that there is marked asymmetry and inconclusive that there is 100% abduction of the left side or the period of abduction is very brief (not maintained) then it will fail post sale scoping at present. Many of these horses go on and race successfully but some do become clinical â€œroarersâ€? within 6-24 months. There is evidence that horses with Grade 1 and 2 scores race more successfully than Grade 3 scores. Treatment of significant laryngeal hemiplegia includes a tie back (laryngeal prosthesis), removal of the affected cartilage (arytenoidectomy), nerve implant, and experimentally pace maker type implants. Success rates for tie backs are fair to good (50-75%) depending on age and what the horse has been capable of doing prior surgery. Right laryngeal hemiplegia Right sided hemiplegia is unusual and may be secondary to nerve damage from abs cessation, guttural pouch disease, incorrect injections, and congenital malformations of the laryngeal cartilages. Treatment includes medical therapy but surgery is required for malformations and unresponsive cases but carries a poor prognosis. Arytenoid Chondritis Arytenoid chondritis involves inflammation and infection of the arytenoid cartilage. The causes are unclear but many likely occur secondary to infection in the upper respiratory tract and evolve - 137 -
from a mucosal lesion/pustule. Infection with normal movement can be treated successfully with local and systemic anti-inflammatories and antibiotics usually over many weeks. Persistent cases may require local debridement of granulation/infected tissue. Some pustules can be drained by interference with the endoscopy or biopsy forceps. Chronic cases causing deformation of the cartilage and therefore affecting movement and abduction will cause noise and exercise intolerance. These cases may improve with medical therapy and can race but may well require surgical removal of the affected cartilage with a guarded to fair prognosis (25-50%). Epiglottic entrapment Epiglottic entrapment involves tissue below the epiglottis (aryeppiglottic fold) moving above it (becoming dorsal to it) and entrapping the tip of the epiglottis and cause exercise intolerance. The entrapped membrane may become thickened and ulcerated. Some entrap intermittently so could be missed at resting endoscopy but most are persistent and easily seen. Treatment involves transection of the entrapping tissue with a laser via the scope or with a curved bistoury knife via the mouth or nose followed by medical therapy and carries a very good prognosis. Epiglottitis Epiglottitis involves infection and inflammation of the epiglottis and is treated with local and systemic anti-inflammatories and antibiotics and carries a good prognosis. Other epiglottic diseases include epiglottic hypoplasia and flaccidity and subepiglottic cysts (dealt with in pharyngeal cysts), epiglottic retroversion and axial deviation of the aryepiglottic fold (both the latter seen on a treadmill only). References Vet Clinics North America Equine (2003) 19 Respiratory Disease, Eric J. Parente, Editor Barakzai S.Z., Dixon P.M. (2011) Correlation of Resting and exercising endoscopic findings for horses with dynamic laryngeal collapse and palatal dysfunction. Equine Vet Journal 43, 18-23.
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Laparoscopy in the mare Laparoscopy uses a laparoscope (large type arthroscope) or endoscope to perform minimally invasive key hole surgery. Compared to large open incisions laparoscopy is quicker to perform once the techniques are learnt and practiced, allows more rapid recovery, enables some procedures to be done without the need for general anaesthesia, and gives opportunity for new techniques and procedures that would not be possible to be carried out otherwise. Disadvantages include the extra cost of specialized equipment and the dangers that can arise when performed in the sedated standing horse. Laparoscopic procedures in use in horses include abdominal and chest exploration, cutting of adhesions (scarring between pieces of intestine following colic surgery); inguinal and umbilical hernia repair and removal of infected umbilical structures in foals and repair of ruptured bladders in foals and mares; cryptorchidectomy (testicle removal in rigs); bladder stone removal; removal of diseased spleens and kidneys; examination and repair of rectal tears; closure of the nephrosplenic space; laparoscopic assisted colopexy to prevent large colon displacements and volvulus; and specifically in the mare, ovariectomy (normal and tumorous ovaries), oviduct examination and prostaglandin gel application, embryo transfer procedures, and uteropexy.
Ovariectomy Laparoscopic removal of both normal and diseased ovaries (e.g. granulosa theca cell tumours) can be performed. Techniques for both recumbent mares under general anaesthesia and for standing sedated mares under local anaesthesia are well described. Approaches via the ventral abdomen, flank and vagina have been utilized. Both hand assisted and solely instrumental procedures are possible. Methods for transection of the vasculature in normal ovaries include various types of electrosurgery (Ligasure and bipolar and monopolar electrocautery), ecraseur devi ce, vascular clips, staples, and various suture loop systems. Advantages over standard surgical removal include better exposure for ligation in ovarian tumour removal and the ability to perform the procedure more safely in the standing mare.
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Uteropexy There are many factors that alter the efficacy of the uterus to clear fluid and debris from the lumen. The normal position of the uterus is horizontal but in middle aged and old mares there is stretching of the uterus and the supporting broad ligament resulting in a more pendulous downward sloping uterus from the cervix downward to the tip of the uterine horn. This adversely affects the ability of uterine contractions to fight gravity and clear fluid causing infertility. Uteropexy involves the lifting of the uterus by suturing it in a more elevated position on the broad ligament. The broad ligament or mesometrium attaches or suspends the uterus to the roof of the abdomen. The procedure is performed in the standing sedated mare and with local anaesthesia of the skin and internally in the mesometrium/broad ligament. Feed bulk is reduced over a few days then feed withheld for 24 hours prior surgery. The left horn is approached from the left flank and the right from the right flank. A laparoscope and two instrument portals are used. Either a laparoscopic needle holder is used or more recently an Endo Stitch device adopted from human surgery (for closure of uterine defects and pelvic support surgery in women) is used. The distance of imbrication onto the mesometrium or broad ligament at the level of the uterine body is about 2-3 cm of elevation and by the tip of the uterine horn between 8 to 12 cm due to the dropped lower level of the horn. Prostaglandin gel can be dispensed easily onto the oviduct at the end of the imbrication. The muscle and skin incisions are then closed. Medical support includes antibiotics, anti-inflammatories (Finadyne) and intravenous fluids during surgery due to the length of the procedure (2-4 hours). The procedure is technically demanding with many possible complications including: pain due to placement of the scope retroperitoneally (not completely in the abdomen) or too close to the nerves along the back of the rib and sometimes reaction to the needle passage in the broad ligament; difficulty in knot tying within the abdomen; difficulty in retrieval of the small Endo Stitch needle from the uterus wall and suture and needle breakage; obscured visibility from gas/ingesta distended bowel and air under the mesentery; and recognized possible complications of bowel penetration and wound infection from abdominal laparoscopic surgery. There is a potential increase in the chance of broad ligament haemorrhage due to the scarring from the imbrication but I think the chances of this happening are far less with the suturing technique afforded by the - 140 -
Endo Stitch device than with the original technique using a laparoscopic needle holder and large needle. Viewing the left uterine horn 6 weeks post-surgery in one mare showed no evidence of a significant scar along the broad ligament. There is also concern for return to the original sagging position of the uterus after foaling. There are reports from the pioneers of the procedure of second pregnancies and no reports of an increased incidence of haemorrhage. The cost of the procedure is prohibitive in some mares. A further encountered and serious complication is failure of the procedure to achieve pregnancy despite apparent functional and anatomical improvement in uterine behaviour. Our res ults for conception have been disappointing having not mirrored the Northern Hemisphere results which have returned about 80% pregnancy. We have not had a pregnancy in 7 mares that have been served with one mare not served as yet. All mares have had a horizontally positioned uterus at the end of the procedure and at subsequent reproductive examinations. In one mare a postsurgery re-laparoscopic look at a left side uteropexy showed a nicely elevated uterus. After failure to conceive subsequent uterine biopsies showed severely chronically inflamed uteri. Only one mare with a mild to moderately affected uterus has undergone a uteropexy and she will not be served until next season. It is likely the mares we have performed the procedure on would still have had the surgery even if biopsies had been performed pre-surgery due to the expense of the mares and poor breeding history (empty for 2 to 7 years). Despite the poor results for pregnancy we believe the procedure does have a role in the treatment of a certain group of problem mares before their uterus becomes too damaged. There is no doubt fluid retention has been dramatically less and usually insignificant at post surgery examinations. The protocol we now follow is a uterine biopsy prior surgery to assess the state of the uterus to gauge the prognosis. We would still perform the procedure on a severely chronically inflamed uterus in a well-bred expensive mare as a last resort but our more preferred mare would be older to middle aged, empty the previous year or two, a history of fluid retention, and a mild to moderately inflamed uterus at worst with preferably a greater acute than chronic inflammatory picture. A study is underway comparing the uterine health with subjective values pre and post uteropexy. The long term effect of this surgery also needs evaluation. Oviduct examination, prostaglandin gel deposition, embryo collection and transfer of gametes.
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Minimally invasive laparoscopic investigation of the oviduct for visual assessment and flushing of the oviduct to evaluate disorders of the oviduct is a recent breakthrough in broodmare management. Diseases found at post mortem include adhesions, cysts, and collagen masses. In a recent study the diagnostic flushing of the oviduct did not appear to affect the ongoing fertility of the mares but larger numbers would need following. Application of prostaglandin gel onto the oviduct is a straight forward procedure that is easier to perform than flushing and is less invasive but is not conclusively diagnostic. Artificial breeding involving laparoscopic embryo collection and flushing of gametes is a further avenue available in non- thoroughbred/non-standardbred breeds. We thank the owners of the mares, the studs and the reproductive veterinarians for their help and support in evaluating a new procedure and hope some benefits occur soon for all concerned. Particular thanks to Dr. Allan Gunn for making us push beyond our normal boundaries. References Equine Diagnostic and Surgical Laparoscopy. (2002) Fischer AT. WB Saunders Co, Philidelphia. Brink P, Schumacher j, Schumacher J. (2010) Elevating the uterus (uteropexy) of five mares by laparoscopically imbricating the mesometrium. Equine Vet J 1-5. Kollman M, Rotting A, Heberling A, Sieme H. (2011) Laparoscopic techniquesfor investigating the equine oviduct Equine Vet J 43, 106-111.
Conformation and lameness in the racehorse. Conformation and lameness in the racehorse are intertwined. Conformation assessment should be in your bag of tricks at yearling sales particularly when purchasing a yearling to race as an early 2yo. Poor conformation does not always mean a horse will suffer lameness.
does not mean your purchase will not suffer lameness either. Conformation, good or bad, does not mean a horse will perform well. However certain conformational faults cause consistent lameness problems. There appears to be hereditary aspects of conformation. The dam seems to play a larger role in offspring conformation relative to the sire. It is thought part of the reason for this is many fillies - 142 -
become broodmares early due to lameness from conformation faults which are then passed to the offspring whereas the sires tend to have to have raced longer and successfully to be chosen as sires so likely have conformation that has stood the test of time (but not always). Conformational faults that appear to be hereditary include toe in and toe out conformation, back at the knee, offset knees, outward rotation, sickle and posty upright hocks. Interestingly there are certain lameness conditions particularly of the carpus and hock that appear hereditary in lines of horses that have normal conformation. In the 1980’s one stallion seemed to throw an inordinate number of progeny that suffered sesamoiditis. Conformation changes with age up to 2-3 years old. Fetlock varus can deteriorate in apparently normal foals and weanlings. Carpal varus and valgus can change through to beyond yearling age and offsetness to 3 years of age. Hoof angle varies until 2 years of age naturally after which any changes may be farrier induced. Conformational issues and associated types of lameness (supported and anecdotal) include:
Upright/posty hocks and proximal suspensory desmitis, fetlock arthritis, upward fixation of the patella.
Sickle hocked (curb) and lameness in the lower hock joints and plantar soft tissues (plantar ligament injury or curb).
Cow hocked/outward rotation cause not so much lameness but more gait abnormalities/interference.
Marked fetlock varus/pigeon toes behind can lead to fetlock and pastern arthritis and uneven foot wall/sole bruising.
Offset/bench knees can contribute to carpal and fetlock lameness.
Increase in carpal valgus is protective compared to straight or bowed knees (the latter is a major career limiting issue).
Too much/severe valgus can overload the inside of the carpus and cause medial splints.
Too severe valgus or varus in the knee can cause catastrophic carpal bone fractures.
Pigeon toes /varus fetlocks predispose to arthritis of the carpus and fetlock and lateral sesamoiditis and suspensory branch issues.
Long shoulders had reduced incidence of forelimb fractures in one study but increased incidence of proximal P1 chips and carpal lameness. - 143 -
Increased length from elbow to ground increased carpal chips.
Increased toe length strongly increased carpal chips.
Upright/clubby feet increase toe soreness.
Upright pastern/foot angle may lead to foot lameness and tendonitis.
Broken back foot/pastern axis may lead to underrun heels and broken forward axis can cause increased pressure on the supporting soft tissue of the fetlock.
Long sloppy pasterns increase the incidence of forelimb fracture and more specifically carpal chip fracture.
Back at the knee can cause carpal chip fractures due to tendency to hyperextend when fatigued.
Offset knees and carpal chip fractures.
Horses taller behind than in front have increased forelimb issues.
Horses disproportionally heavier behind or in front (unbalanced) predispose to lameness at the heavier end.
Steep short shoulders with upright pasterns are predisposed to lower limb lameness.
Base wide stance with narrow chest overloads the inside of the limb causing lameness.
Base wide, toed out and too much valgus overload the inside of the foot and cause misshapen feet.
Over at the knee and proximal suspensory and carpal canal issues.
References Conformation and Lameness: Ross MW and McIlwraith pge 15-32 In Dyson The Relationship between Conformation and Lameness Stashak TS pge 72-99 In Adam’s Lameness in the Horse
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Feeding on the Stud Farm Lecture Nine DR. PETER HUNTINGTON, DR. JOE D. PAGAN AND DR CLARISSA BROWN DOUGLAS Kentucky Equine Research, www.ker.com
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Broodmare Stages of Pregnancy A broodmares' feeding program should be divided into three separate stages. Stage one is early pregnancy, from conception through the first seven months of gestation. Barren mares and pregnant mares without foals by their sides fit into this nutritional category. Stage two encompasses the last trimester of pregnancy, which is from around seven months of pregnancy through foaling. Stage three is lactation, which generally lasts five or six months after foaling. The nutrient requirements for these three stages differ markedly and adjustments should be made in the mare’s feeding program to accommodate these differences. The most common mistakes made in feeding broodmares are overfeeding during early pregnancy and underfeeding during lactation. The breeder should aim to maintain the mare in optimum condition throughout the year, keeping careful track of fluctuations body condition score and weight. This is referred to as “straight line nutrition” and is the best way of ensuring correct development and growth of the foetus and nutritional health of the mare. Stage 1: Early Pregnancy To feed the mare properly during pregnancy, it is important to understand how the foetus develops throughout the gestation period. Contrary to popular belief, the foetus does not grow at a constant rate throughout the entire eleven months of pregnancy. Figure 1 illustrates a typical growth curve for a foetus expressed as a percent of birth weight. The foetus is very small during the first five months of pregnancy. Even at seven months of pregnancy, the foetus equals only about 20 percent of its weight at birth. At this stage in pregnancy the foetus equals less than two percent of the mare’s weight and its nutrient requirements are miniscule compared with the mare’s own maintenance requirements. Therefore unless she is lactating, the mare can be fed essentially the same as if she were not pregnant at all. An ideal diet may comprise of pasture alone with the addition of a vitamin and mineral supplement to balance nutrient shortfalls in the pasture (Table 1 & 2). Obviously if pasture is poor or scarce, additional hay or chaff should be fed a rate of at least 1-1.5% bodyweight per day or ad lib throughout pregnancy and lactation if hay quality is average to poor.
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All too often, the well-meaning mare owner greatly increases feed intake after the mare is pronounced in foal, reasoning that she is now â€œeating for two.â€? This is not only unnecessary, but may lead to obesity and problems at foaling time. Obesity in broodmares is a serious problem, not only affecting the maresâ€™ fertility and ability to conceive, but seriously risking the health of the foetus. Over conditioning your mare at this stage may increase the chances of the foal exhibiting developmental orthopaedic diseases after birth. This is particularly true where mares have access to high quality pasture during early pregnancy. If pasture quality is high, it may be necessary to restrict grazing by means of stabling or muzzling for part of the day. Access to pasture or hay should not be denied for longer than eight hours at a time to prevent digestive upsets. By the same token, it is very important in early pregnancy that the mare does not go into negative energy balance and loose condition. Owners of picky eaters, poor doers and lactating mares with foals at foot need to be especially vigilant of body condition. Mares in poor condition are at increased risk of pregnancy loss. If a mare is a good milker and pasture is dry and scarce, additional provisions should be made to ensure that she does not begin to loose condition.
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Late Pregnancy After seven months of pregnancy, the foetus begins to develop rapidly. At this point, its nutrient requirements become significantly greater than the mareâ€™s maintenance requirements and adjustments should be made in the mareâ€™s feeding program. Table 1: Straights based diet. Based on a 5yo 500kg mare on moderate to good quality pasture. If pasture is too good, grazing restriction may be necessary, if pasture is poor; supplementation of hay or chaff may be required. Pregnancy Stage
Oats kg All-Phase Pellet kg
Pasture or hay kg Salt (loose or DM block) g
1. Early Pregnancy
2. Late Pregnancy
Table 2: Pre-mixed broodmare feed diet. Specialised broodmare feeds can vary considerably so check feeding recommendations on the bag and check ingredients to ensure correct DE, Protein, Calcium, Phosphorus, Copper, Zinc, vitamin and trace mineral requirements are being met. Remember that if good doers are fed below recommended levels on the bag, a vitamin and mi neral supplement may also be required. Pregnancy Stage
Breed N Grow kg
Pasture or Hay kg DM
Salt (loose or block) g
1. Early Pregnancy
2. Late Pregnancy
Digestible energy (DE) requirements only increase about 15 percent over early pregnancy. Protein and mineral requirements increase to a greater extent. This is because the foetal tissue being synthesised during this time is quite high in protein, calcium and phosphorus. During the last four months of pregnancy, the foetus and placenta retain about 77 grams of protein, 7.5 grams of - 148 -
calcium, and 4 grams of phosphorus per day. Trace mineral supplementation is also very important during this period because the foetus stores iron, zinc, copper, and manganese in its liver for use during the first few months after it is born. The foetus has developed this nutritional strategy of storing trace minerals during pregnancy because mareâ€™s milk is quite low in these elements. New Zealand researchers studied the effect of copper supplementation on the incidence of developmental orthopaedic disease in Thoroughbred foals. Pregnant Thoroughbred mares were divided into either copper supplemented or control groups. Live foals born to each group of mares were also divided into copper supplemented or control groups. The four treatment groups therefore were: 1) mares supplemented with copper (0.5mg/kg body weight), but their foals were not supplemented; 2) both mares and foals were supplemented with copper; 3) mares were not supplemented, but their foals received supplementation; and 4) neither mares nor foals received supplementation. Copper supplementation of mares was associated with a significant reduction in the physitis scores of the foals at 150 days of age. Foals from mares that received no supplementation had a mean physitis score of 6, while foals out of supplemented mares had a mean score of 3.7. A lower score means less physitis. There was no significant effect of copper supplementation of the foals on physitis scores. There was a significantly lower incidence of articular cartilage lesions in foals from supplemented mares. However, there was no significant effect of copper supplementation of the foals on articular and physeal cartilage lesions. The amount of copper consumed per day should total around 175mg per day for a 500kg mare. Remember that some copper (around 50â€“ 75mg per day) will be supplied from pasture or alternative forage sources too although amounts depend on pasture or forage quality. Vitamin A has been found to be of critical importance to the late pregnant mare. Studies by Dr Kathleen Crandell of Kentucky Equine Research showed that if mares are maintained on hay alone with no green pasture and no vitamin A supplementation, the subsequent growth rates of their foals is reduced significantly. As hay is stored over a period of weeks and months, itâ€™s vitamin A content is drastically reduced. If pasture is scarce, and the mare relies on hay as her major forage source, supplementation of vitamin A may be necessary to avoid this scenario.
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Additionally, selenium and vitamin E supplementation in late pregnancy has been shown in recent research to enhance immunity in both the mare and foal. Antibody levels were higher in foals of mares receiving 3mg selenium and 1600 IU vitamin E /day as opposed to controls (only 1mg selenium and 800 IU vitamin E /day). Selenium may also help the mare by reducing the risk of retained afterbirth as shown in cows. To ensure that mares are receiving enough copper, vitamin A, selenium and vitamin E in their diets at this stage of pregnancy, choose either pre-mixed feeds or supplements containing appropriate levels of these vitamins and minerals as detailed on the bag or bucket. Mares in late pregnancy are often overfed energy in attempt to supply adequate protein and minerals to the developing foal. This seems to be especially true of warm-blood and draught horse breeds. If the pregnant mare becomes fat during late pregnancy, she should be switched to a feed that is more concentrated in protein and minerals so that less can be fed per day. This will restrict her energy intake while ensuring that she receives adequate quantities of other key nutrients. Mares in the late stages of pregnancy can be fed either a complete mixed feed desig ned for broodmares eg BARASTOC BREED’N’GROW and balanced to provide all the vitamins and minerals required by the mare at this stage or an owner designed diet in conjunction with a commercially available balancer supplement. Rates of feeding depend on the size and age of the mare and the recommendations for the particular brand of feed. Some mares can survive on pasture alone with a vitamin and mineral supplement even in late pregnancy and not lose condition without any detriment to the foal. Good horse sense and personal knowledge of the mare and her condition in relation to feeding should always be the first guide when designing feeding schedules. If owners prefer to feed straights, oats are always the first choice grain to feed for energy along with a balancer supplement such as KER All-Phase PELLET to ensure adequate vitamin and mineral intake ( Table 1 & 2).
Lactation After foaling, the mare’s nutrient requirements increase significantly. During the first three months of lactation, mares produce milk at a rate equal to about 3 – 4 percent of their body weight per day. Some mares milk so well that whilst the foal grows quickly strong, the mare begins to loose condition, using her own reserves to supply her foal. This may make it difficult for the mare to conceive again and subsequently retain the foetus due to malnutrition. All efforts should - 150 -
be made to keep the mare in good condition during lactation and this is the time that the art of condition scoring on a regular basis can reap rewards. Mare milk is rich in energy, protein, calcium, phosphorus and vitamins. Therefore, the mare should be fed enough grain to meet her greatly increased nutrient requirements. Mares in early lactation may require up to 8 kg of grain per day depending upon the type and quality of forage they are consuming but as previously mentioned, some mares of particularly well doing breeds can be successful milkers on good pasture and a vitamin and mineral supplement alone. The aim should be to use the best quality forage, and keep grain levels down to avoid potential digestive upset. If straight grains are being used, the grain should be fortified with additional protein, minerals and vitamins to meet the lactating mare’s needs. There are a number of commercially available balancer supplements that can be used to fortify grains, but check labels to ensure adequate intake of each constituent. Again, the grain portion can also be in the form of a complete mixed feed to ensure balanced and convenient nutrition (Table 1 & 2). Trace mineral fortification is not as important for lactating mares as for late pregnant mares because milk contains low levels of these nutrients and research has shown that adding more to the lactating mare’s diet does not increase the trace mineral content of the mi lk. Once the foal starts eating from the mares feed bucket, however, a well fortified feed is important to ensure adequate intake of vitamins and minerals by the foal, unless the foal is being creep fed, in which case only the foal’s diet really needs to be supplemented. Calcium and phosphorus are the minerals that should be of primary concern during lactation so lucerne hay is the forage of choice due to its high calcium content. It may benefit to the foal to supplement the mare with additional calcium and phosphorus during lactation. Grain intake should be increased gradually during the last few weeks of pregnancy so that the mare is consuming nearly the amount that she will require for milk production at the time that she foals. A rapid increase in grain should be avoided at foaling time because this may lead to colic or founder. After about three months of lactation, milk production begins to decline. At this time, grain intake can be reduced to keep the mare in a desirable condition. It is often beneficial to cut down the mares grain ration just prior to weaning to help the mares’ milk to dry up when the foal is taken off.
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The Thin Barren Mare This type of mare may have a multitude of reproductive problems including lactational anoestrous and the inability to get back in foal. You want to get this mare cycling regularly in August and have her covered in early September. It is advisable to get this mare in good condition (> CS 3) going into the breeding season and perhaps do some nutritional flushing in the thin mare along with having the mares under lights and with an individual feed program starting June 1. Flushing refers to having the mare in an ascending plane of nutrition and gaining weight when she is bred. Though there is little experimental data that shows flushing to increase the reproductive efficiency of the mare, but common wisdom and experience tells us that flushing has a valid place in the nutritional management of the thin mare. This is the case with most maiden mares, especially those that are retired to stud just before the season.
The Mare with Poor Reproductive Conformation Mares with poor reproductive conformation are far more likely to ‘windsuck’ and have reproductive inflammation and infection, which reduces their reproductive efficiency. This type of mare will usually be ‘caslicked’ after service to limit contamination of the uterus, but keeping the mare in good to fat condition (CS 3 to 4) leads to fat deposition around the vulva and improved reproductive conformation. This can improve the reproductive efficiency of this type of mare
The Fat Mare After having read the previous sections it would be tempting to think the mare should be maintained in fat (CS 4 and above) condition after weaning. This approach has some drawbac ks even though it may look good for the amateur mare owner. The fat mare has an increased risk of having a foal with bent legs (angular limb deformities) that could, if not treated effectively, limit the foal’s athletic potential. The other drawback of having your mare too fat is that she may be difficult to get back in foal. Consider the situation of the fat mare that has been pampered at home with 3 feeds a day. She is sent to the stud just before foaling and suddenly she’s mixed with a new group of mares, is in a new environment and on a new feed program. The mare looses weight and doesn’t cycle as well or may shut down entirely. So avoid getting your mare fat even though it may look more pleasing to have her in show condition. - 152 -
In conclusion, mares should be fed differently during early pregnancy, late pregnancy, and lactation. By understanding the mareâ€™s nutrient needs during each stage of her reproductive cycle, an intelligent and cost effective feeding program can be designed and implemented. Remember to avoid overfeeding during early pregnancy and underfeeding during lactation. Be aware of differences in nutritional requirements between breeds. Know that the season affects pasture quality and quantity, which can drastically affect your mares supplementary feed requirements. Make condition scoring a routine and act on the slightest noticeable changes aiming always to keep the mare at a consistent level of healthy body condition.
Stallion Fertility and Nutrition Like all horses, a stallion needs a balanced diet with adequate, but not excessive amounts of nutrients for optimal health and fertility. Stallions are commonly overfed energy and they get fat. This can lead to reduced fitness, libido and fertility and make the horse prone to soundness problems, insulin resistance and laminitis. Unfortunately many older stallions suffer from laminitis or die from heart attacks and both conditions may relate to being too fat. So adjust the feed and work to keep your stallion in good, but not fat condition. Whilst there are no prepared feeds designed especially for stallions in Australia, there are a number of quality feeds that if fed according to directions will supply a balanced diet. If you are mixing your own feed, addition of the KER All Phase feed balancer pellet will fill in the nutrient gaps in a basic diet of grains and forage. If you need help to maintain condition and a shiny coat in a breeding stallion the stabilised rice bran Equi-Jewel is a great supplement. Equi-Jewel is a very palatable source of rice bran oil and supplies â€˜coolâ€™ safe energy. It also contains high levels of natural vitamin E and organic selenium, important antioxidants for stallions. Rice bran oil contains gamma oryzanol which also has antioxidant properties. Reactive oxidative species (ROS) and free radicals cause oxidative stress to sperm and play an important role in sperm function. Reduced motility is a good indicator of oxidative stress and chilling or freezing semen increases oxidative stress. The detrimental ROS can be neutralized by antioxidants in semen. Stallions may benefit from supplementation with the antioxidants vitamin E or selenium, especially if they are being collected for chilling or freezing semen where survival of - 153 -
motile sperm is vital. Low levels of selenium in sperm are associated with changes in DNA and reduced fertility. Higher blood levels of antioxidants may boost antioxidant protection in the seminal plasma, and increase the survival of progressively motile sperm. Feed from many areaâ€™s of the country have very low levels of selenium, so the feed or supplement fed to your stallion should supply at least 2 mg selenium per day and organic selenium is the preferred source. Recent research has shown that natural vitamin E has much greater bioavailability than synthetic forms so it makes sense to supplement stallions with high levels of natural E, especially if green pasture intake is limited. KERx Nano E is a new nanodispersed water soluble liquid source of natural Vitamin E that has been shown to be more effective than other forms in boosting blood levels of vitamin E. Higher blood levels means better antioxidant protection in semen and sperm. It is the vitamin E supplement of choice for the stallion. Recent research in the US has demonstrated benefits in supplementing the diet of sub fertile stallions with omega 3 fatty acids from fish oil sources. Several studies have concluded that stallions with poor sperm survival and motility after chilling or freezing, can benefit from added long chain omega 3 fatty acids EPA and DHA from fish oil. These fatty acids are important components of sperm membranes and most modern diets contain low levels of these fatty acids and their precursors. Positive results have included increased progressive motility, increased % morphologically normal sperm and even increased sperm output. It has been shown that supplementation with fish oil increases the levels of DHA and EPA in sperm cell membranes and this helps protect against cold shock. KER EO-3 is a new palatable and stable fish oil product which contains 25% EPA & DHA and is the supplement of choice for supplying these long chain omega 3 fatty acids. The recommended dose is 60ml per day for normal stallions and 90 â€“ 120 ml for horses with sub fertility. Like all horses, stallions should be fed a simple balanced diet, but they do have some special needs and the sub-fertile stallion can benefit from some extra attention to maximise fertility.
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Growing Horses Weanlings One of the most challenging aspects of the feeding program on a breeding farm involves weanlings. The weanling faces the stress of removal from its dam, mixing with a group of young horses and sorting out a pecking order all at a time of year when weather conditions are tending to deteriorate and cold nights or wet days are more likely to occur. Yet commercial demands mean that weanlings must continue to grow at a rapid rate so that they can reach growth targets for weanling or yearling sales. The weanling has similar nutrient requirements to the yearling but eats a lot less feed, so that the required nutrients must be packaged in a more concentrated form. Weanlings have a significant risk of getting Developmental Orth opedic Disease (DOD) such as physitis of the fetlocks, contracted tendons, bone cysts or OCD. The first factor to consider is age of weaning. The mare’s milk production peaks at two months, and then there is an increasing gap between the foal’s needs and what the milk can supply. This gap can be supplied by pasture or the mare’s hard feed. A foal can be weaned from 4 months of age and a recent study showed that weaning was less stressful for four month old foals than it was for six month old foals, when stress was judged by the growth setback at weaning. Some foals that are doing too well, or not well enough or have signs of DOD may need to be weaned earlier than the rest of the group. Another factor is how the mare is doing and early weaning may be needed if the mare is falling away in condition as she feeds an older foal. One factor that has a big influence on the growth of weanlings is familiarity with the post weaning feeding program prior to weaning. A foal that is used to the hard feed will adapt to conditions much better after weaning. This means that if your mares are not being fed or are being fed differently to the weanlings feed, then you will need to creep feed your weanlings. Creep feeding does not imply force-feeding. Creep fed foals should be given no more than 1.5- 2kg of grain or concentrates per day starting at three months of age. To achieve optimum growth rates, the weanling needs to consume significant amounts of energy, amino acids, protein, and minerals yet its restricted appetite means that it needs a concentrated nutrient package. Commercial weanling feeds such as BARASTOC BREED N GROW are more - 155 -
concentrated sources of nutrients than feeds for adult horses such as mares. They have higher energy and protein content along with elevated mineral levels, so the requirements of the weanling can be met in a 2.5 –3kg feed per day. In sweet feeds, the processing of barley and corn is desirable and the steam flaking used in feeds increases the digestibility of energy in these grains. The average 6 month old 250 kg weanling growing at 1 kg per day will require about 2.5-3 kg of a weanling feed per day for satisfactory growth. This equates to 1% body weight and will need to be fed twice a day. Remember you need to allow for variation in intake so if you have eight weanlings in a paddock provide them with nine feeds. Allow two weanling feeds for any granny or minder that you have in the group. If you have large numbers of weanlings , the older and bigger weanlings will need more feed than the younger group, so provided you match up your mobs right, you can vary the intake appropriately. As the weanling has a restricted appetite it is important that the feed you give them is palatable. Sweet feeds have been shown to have greater palatability than pellets or extruded feeds, and the use of a sweet feed such as BARASTOC PREPARE or LEGEND may ensure that all weanlings eat enough hard feed to supply their nutrient needs. The advent of pre sale x-rays has focused attention on DOD and other bone problems in yearlings. If you feed high grain intakes to achieve maximal growth you will increa se the risk of DOD problems being found in yearlings. But if you don’t feed any grain, you are unlikely to meet market expectations for growth and condition. Some hard feeds are safer to feed than others, as research has shown that feeds that have a lower Glycemic Index (the glucose response after feeding) are associated with a lower incidence of OCD. Since this research was completed KER have developed some specialised low glycemic index feeds in several countries and investigated the Glycemic Index (GI) of many other feeds. In one Australian study, the KER Low GI Cube was shown to have a significantly lower GI than oats or 2 extruded feeds. However, it is important to remember that nutrition is only 1 of the risk factors involved in the development of OCD. The quality and quantity of pasture available will determine what sort of hay you need to feed and how much hay and chaff weanling needs. Green pastures will usually contain close to or over 20 % protein, so this means protein and amino acid supply will be met from the combination of pasture and an appropriate grain mix. In the case of plentiful pasture resulting from irrigation or autumn rain you can mix a little bit of chaff in with the grain, but you don’t really need to supply hay, apart - 156 -
from days of rain and cold weather. On the other hand, if your weanlings are in paddocks with little grass or dry pasture they will need supplementary lucerne or clover hay/chaff to meet their protein and amino acid needs. If you are providing supplementary forage for your weanlings, always use top quality chaff or hay. Lucerne and clover have higher energy, protein, amino acid, and calcium content than grass hay or oaten chaff. This means they are the preferred supplementary forage source if you are aiming for optimum growth. It is not essential to feed chaff, but it does increase the safety of feeding grain to groups of weanlings and the amount of chaff fed should be in proportion to the amount of grain. The aim of weanling feeding is to allow for optimum growth with minimal DOD. If you choose the right weanling feed and feed the appropriate amount there is no need for added supplements, and in fact the use of extra supplements can create nutritional imbalances. Key nutrients such as amino acids, calcium, phosphorus, copper, zinc, manganese and Vitamin E should be provided by the hard feed you use. However if you have your own oats in a silo and need a supplement to mix with them, then the KER ALL PHASE BALANCER PELLET offers you great flexibility and an easy way to feed a balanced diet. Weanlings that are too heavy or have early signs of DOD can benefit from a period with no grain, but having their amino acid and mineral needs supplied by the ALL PHASE PELLET as a supplement to forage. Putting these weanlings on a plain grass or hay diet will be counter-productive as they will be getting a mineral and vitamin deficient diet Weanlings not going to sales are typically fed in a more conservative manner. These weanlings do not have to grow at a maximum rate or look their best at a young age. Instead, breeders are trying to raise young horses that will be sound athletes. Generally the best way to assess the impact of the feeding program of these weanlings is through assessment of body condition. Weanlings should maintain a thrifty appearance in which the horseâ€™s ribs can just be seen, or are not seen but can be easily felt. Monitoring weight along with an accurate condition scoring system allow for the assessment of quality and quantity of growth. We have developed a specialized software program Gro-Trac to allow breeders to record and monitor growth and link that with dietary changes necessary for optimum growth. The amount of grain necessary to maintain a thrifty appearance varies with the individual weanling, and the available quality and quantity of forage. Being able to feed weanlings as individuals and make necessary feeding adjustments is very important, so donâ€™t feed all groups the - 157 -
same. â€œGood -doingâ€? weanlings should be kept from becoming fat by being fed a low-intake, lowcalorie source of essential protein, vitamins and minerals. On the other hand, weanlings that are large with much growth potential can consume normal amounts of fortified concentrate. A general rule of thumb for feeding weanlings is one kg of fortified grain per 100 kg of body weight, up to a maximum of 3 kg per weanling per day. If you need extra energy above this level, it is best to supply it from fat eg oil or Equi-Jewel or from a high quality forage. It is important to remember that foals will not all weigh the same at a given age. There are many good ways of feeding weanlings that work in different situations, but horses should be fed as individuals for the best results.
Feeding and Fitting: The Sales Weanling and Yearling There are two groups of horses that are assessed and therefore valued to a large extent on their looks, conformation and the way they are "turned out"; the show horse and the sales weanling or yearling. There are vast sums of money riding in the balance that literally can be made or lost depending on the job that the feeder and fitter does. We have all heard the adage "fat is a pretty color" and seen that some sales and show horses are simply fed all they want to eat and have then gotten too fat. In the modern sales and show arena simply fat is far from being enough. To be really successful in preparing sales horses and show horses the "fitter" must be able to differentiate between fit and fat. It may come as a surprise that one would consider the young show horse and the Thoroughbred sales weanling and yearling in the same context. But let's face it, the horse sale is a horse show and many times horses are worth more on sale day than they will be the rest of their lives. Prepping these horses is a combination of superior nutrition, superior health management, superior and specific exercise and superior genetics, tempered with hard work and attention to detail.
Feeding Preparing a weanling is perhaps the biggest challenge of all. When one prepares a weanling for a show or sale it is vital to understand the nutrient requirements of the horse and the critical balance between feed intake and exercise as they impact on condition and soundness.
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The weanling feeding program should be based on a balanced ration using palatable, easily assimilated nutrient sources that meet the weanling's requirements for protein, energy, minerals and vitamins. Often people fall into the trap of feeding all-grain feeds to weanlings that may encourage fattening but do little to ensure optimum growth and bone development. It is crucial that people understand that "HIGH" PROTEIN DOES NOT CAUSE BONE PROBLEMS! And in fact more cases of acquired flexural deformities and developmental orthopedic disease (DOD) are caused by improper mineral balance and over feeding energy than from any other nutritional cause. The amount of feed that an individual foal/weanling will tolerate is extremely dependent upon the individual and it is crucial to adjust individual feeding levels based on individual performance (growth rate and degree of fatness). It is common to feed a weanling intended for the futurity or weanling sales a minimum of 1 lb of feed per month of age right up until the time of the event. In general one would be best served to feed a 15 - 16 % protein concentrate to these horses in addition to a fat supplement and really good quality clover or lucerne hay that was harvested in early stages of maturity. A high quality/high energy hay is needed for these horses as this maximizes the utilization of fibrous feeds in meeting the energy requirements of these horses and as such decreases the amount of starch the weanling has to deal with. Also, in using a high quality, early cut hay one tends to minimize the appearance of gut-fill that is often associated with a mature hay of high lignin content. Often hay intake is restricted just prior to the show or sale to reduce a pot bellied appearance. In selecting the appropriate concentrate feed for the weanling it is important that the total nutrient profile of the feed be considered, not just the protein concentration. All too often, due to formulation errors on the part of the feed manufacturer or misuse of a feed (primarily cutting a prepared feed with oats) by the consumer, the nutrient/calorie ratio of grain mixes fed to weanlings is all wrong. Horse owners should be educated to the fact that the nutrient profile of a feed designed for a specific class of horses is critical and that by "tinkering" with a feed this balance of nutrients is destroyed. Similarly, feeds formulated for older horses do not get the job done with respect to macro and micro-mineral intake when fed at appropriate levels to meet the young horse's energy requirements. For one thing, a weanlings appetite is much less than an adult horse so you need to have higher concentrations of critical nutrients. Feeds containing heat - 159 -
processed barley and corn are very useful, because the energy in the grain is much better digested and assimilated after steam flaking, micronising or extrusion.. A feed used for weanling sales or show prep should contain added fat from oil, stabilized rice bran or sunflower seeds. This fat is a very concentrated source of energy and helps minimise the grain intake needed, as well as putting a shine on the coat. Beyond the feed bin the real art involved in fitting weanlings is the exercise and "rubbing" they receive. Although not advocating routine lungeing for the sales or show weanling, judicious use of free lungeing, time on the walker and hand walking can be very useful tools depending on the individual. Foals run, romp and play nearly from birth, and to think that a careful program of forced exercise is detrimental and risky is folly. Daily grooming, rinsing with warm water, braiding or banding of manes and conditioning of tails are all necessary for weanlings if optimum condition is to be achieved. Feeding at least 125 ml oil daily or a minimum of 500g stabilized rice bran such as KER Equi-Jewel ( or a higher fat feed ) and a biotin, zinc, methionine coat conditioner eg KER Bio-Bloom for a month before the sale will also really help the coat. As much as 300g of added fat per day has been fed in some instances when it was critical that more energy be provided without increasing starch ( grain) intake. If horses are gradually adjusted to fat intake, a great deal of energy may be fed to the weanling in the form of fat. If you have a weanling with physitis or other DOD it is preferable to feed a high fat rather than a high grain diet, but these young horses still need supplementary protein, minerals and vitamins which is usually fed in the form of a low intake balancer pellet The last thought for the weanling deals with weaning time. In general we have found 5 months of age to be the most ideal time to wean, all things considered. However, it is best to let the individual weanling tell you when to wean. If a weanling is top-heavy and too fat or starts to get upright in the pasterns or show severe physitis, there are good reasons for weaning as early as 3 months of age so that you can carefully control nutrient intake. A general rule of thumb is to wean a foal at least 45 days before a sale or futurity or if that is too early for late foals, wean 5 days before a sale. Forty- five days gives adequate time to get the weanling over the post-weaning slump and into good shape, and five days does not give the weanling time to fall apart.
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Feeding the Yearling Yearlings in some ways are easier to prepare than weanlings. Since we are in most cases talking about horses that are at least 12 months of age there are fewer skeletal wrecks that we can precipitate when we start our fitting or "prep" program. In discussion of the prepping process it is appropriate that we start with the feeding program. Yearlings do best on a 13-14% protein ration balanced for macro and micro-minerals and fat and water soluble vitamins. Feeding rates for yearlings are extremely variable depending on growth history, skeletal size, individual metabolism, actual age and quantity and quality of forage. In the preparation of sales yearlings, hard feed intakes range from 1 kg/day of a supplement pellet to 10 kg/day of grain or a fortified sweet or pelleted feed. Generally it seems to take more feed to get a colt fit than it does a filly. The real key here is realization that "the eye of the master fattens the ox." What works in the feeding program for one yearling may totally miss the mark for another! Comments made concerning hay type and quality for the weanling, apply to the yearling as well. However if you have a short, fat filly that needs to lose weight, choose a lower energy grass hay or oaten chaff rather than rich lucerne or clover hay. But if gastric ulcers are suspected, lucerne hay will provide the best buffering of the stomach acid. Besides the base feed, there are some tools of the trade that fall into the nutrition category. First, always use some supplemental fat. You can use vegetable oil, feed sunflower seeds, or a commercial fat supplement such as EQUI-JEWEL. Suitable oils include corn, soy, canola or vegetable oil, but do not use recycled oil. The manner in which the fat is provided in the diet is a choice for the horseman but in many instances it makes more sense to top-dress the fat rather than use a fat added feed. As for the "grain" portion of the ration, the amount of fat that is appropriate to use is going to be highly individual. This is due to the fact that there are two main reasons that we are using fat to begin with. First there is the hair effect and second there is the energy effect. The hair effect is easy, a minimum of 60g per day of vegetable fat. The use of high levels of fat intake in the yearling is to reduce the amount of starch that must be fed to achieve a specified energy intake. When you reach 5 kg of hard feed intake in the yearling, start to really consider the advantages of supplemental fat. Big, rugged, raw boned yearlings can take as much as 750 ml of vegetable oil or - 161 -
2 kg EQUI-JEWEL per day with absolutely no detrimental effect. Again feeding BIO-BLOOM will help get the gleaming coat you need to stand out from the field and will reduce the time you need to spend grooming the yearling. That saves staff time and costs. In addition to fat, many prep and show rations will contain lupins and beet pulp. Unlike the weanling, there is a real possibility and starch over-load diarrhea, colic, laminitis and behavior problems in the yearling. By using lupins or beet pulp in the feed, one can reduce the amount of starch that a horse has to consume while keeping relatively high levels of energy intake. These sources of highly digestible fibre are fermented in the hind-gut and absorbed as volatile fatty acids therefore reducing the amount of starch that may enter the hind gut un- digested, and contributing to a happy hind gut! Heat processed feeds or components in the feed are also useful they don't reduce the starch intake but they do ensure most of the digestion takes place in the small intestine thus reducing the risk of hindgut acidosis. As hindgut acidosis is so common in sales yearlings on high grain diets, ad lib hay should be fed and the hind gut buffer KERx Equi-Shure can be used as a preventative measure or to yearlings showing signs of hindgut acidosis . Emphasis should always be placed on the individual in terms of feed intake levels and exercise programs. The goal should be individual fitness. That takes an individually tailored feeding and fitting program. It is critical to understand that fit and fat are not the same, and that lotâ€™s of feed without an increase in the work program results in a horse that is patchy in its fat cover and more prone to disorders such as colic, laminitis, physitis and behavior problems. Obviously there are as many tricks of the trade as there are trainers and what techniques work for some may not work for others. The important thing is to design a program and stick to it. Modifications may be necessary along the way to suit individual needs, but the critical aspect of getting this job done is daily attention to detail. One should not get caught in the trap of thinking that there is some magical feed ingredient that is going to turn a sow's ear into a silk purse. Great genetics, good feed and hard work beat steroids, poor genetics and lack of preparation every time. Remember you are preparing a future athlete, not fattening a lamb for market.
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Handling Weanlings Lecture 10 ROSS LINDEMAN, Alphahorse
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Understand Foal Behavior • The foal’s reliance on its mother and her role. • The mare and her role in the foals education and safety. • The foals balance (environmentally). • Approaching a foal: a) In a crush situation. b) In the open. • Restraining a foal. • Learning speed and time frame of a foal. • If they have started to sweat you have gone too far or nowhere. • When to quit.
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What to Expect from a Foal during Education • A foal’s reaction is not personal or calculated. • Attention span. • Being separated from mare. • Leading up (head pressure) • Don’t expect each foal to react exactly the same way for each step of teaching
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Everyday Working Routines that can be Incorporated into the Foals Education • Just standing with the foal while in the crush. • Being conscious of how you move mares and foals when running them in and while moving them in the yard. • Mindful of the working environment i.e. is there too much peripheral activity going on. • Put the time aside to handle horses …if you do not have the time, don’t. • When working with others give the foal an opportunity and have everyone paying attention to the job at hand.
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The Weanlings Behavior and Change of Balance • Mum has gone ….who replaces her? • Approaching a weaner. • Restraining a weaner.
• Learning speed and time frame. • When to quit.
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A Summary of Responsibility • The baby sitter. • Nurturing someone’s investment. • Foals safety. • The safety of others, i.e. farriers and vets. • Foals foundation for the rest of there life. Giving them the tools to cope with the people around him for the challenging future they have ahead of them.
• Just because granddad did it does not make it right. • The horse is just trying to make it through.
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BASIC REPRODUTION OF THE MARE CYCLE AND HORMONAL REVISION; CYCLE MODIFICATIONS PARTURITION IN THE MARE COMMON DISEASES IN THE FIRST THREE DA...
Published on Jul 30, 2011
BASIC REPRODUTION OF THE MARE CYCLE AND HORMONAL REVISION; CYCLE MODIFICATIONS PARTURITION IN THE MARE COMMON DISEASES IN THE FIRST THREE DA...