Florida-breds Around The Country

Stakes, Allowance, Allowance Optional Claiming and Maiden Special Weight statistics below are listed for the month of Jan. 2023 for win, place and show, alphabetically by horse name.

BY HEATHER SMITH THOMAS

Mares often exhibit changes in behavior during estrus cycles and sometimes the behavior interferes with their management, training or performance. Often when a mare behaves badly, her attitude and actions are blamed on estrus, but in some instances, the unwanted behavior may stem from another problem. Figuring out what is causing the behavior should be the first step in trying to address it.

Dr. Ryan Ferris, Summit Equine Inc. at Gervais, Oregon, says a normal cycle consists of roughly seven days of estrus and a 14 day period of diestrus (when she is not in heat).

“The behavior of a mare in diestrus generally is not objectionable. During the seven-day period of estrus, however, she may squeal at other horses, urinate small amounts frequently, and be easily distracted by other horses; her mind isn’t on her job.”

Behavior is often most frustrating during spring transition out of anestrus, when mares start cycling again.

“The mare is growing follicles and there is a lot of estrogen circulating,” Dr. Ferris said. “This causes estrus behavior but there is no progesterone—no diestrus phase—because the mare doesn’t ovulate until the end of this transitional phase,” he says.

Dr. Peter Sheerin, Rood and Riddle Equine Hospital in Lexington, Ky., says it’s important to determine if unwanted behavior is related to estrus or not.

“If it is related to the estrus cycle it should be happening every 21 days or so, and if the bad behavior continues in winter, it’s likely not related to reproductive cycles,” Sheerin said. “We need a description of the behavior. Many mares, when in pain or angry, may urinate and swish their tails repeatedly. And people think they are heat. Posture and presentation of a mare that is urinating when she is in heat is different from a mare that is upset.

“The mare in heat will squat, with tail raised, pass a little urine and may also ‘wink’ the clitoris.”

By contrast, the angry mare usually has her tail swinging like a windmill and there is urine everywhere. She may also clamp her tail.

“After evaluating behavior, we look at the mare’s reproductive tract via palpation and ultrasound—to see if there are any abnormalities.

Do the ovaries look normal? During breeding season, she should either be in heat or out of heat and her ovaries would contain appropriate structures related to the stage of her cycle,”

Sheerin said. “If she’s in heat, she should have a big follicle and estrus edema, and her cervix would be relaxed. If she is out of heat she should have a corpus luteum (CL) in the ovary and her cervix tightly closed, with no edema in the uterus. We can also pull blood and look at progesterone levels. A mare that is in diestrus should have elevated progesterone.”

“Abnormal behavior can also be associated with an ovarian tumor,” Ferris said. “These tumors secrete a range of hormones that may cause the mare to exhibit signs of persistent estrus, or she may never show estrus. Some of these mares may have stallion-like behavior and become aggressive toward other horses,” he said.

In a group, these mares may try to herd other horses around or mount other horses.

Mares with an ovarian tumor that exhibit stallion-like behavior, will act and sound like a stallion and often develop a cresty neck.

“With those traits, we’d suspect a granulosa cell tumor or a granulosa theca cell tumor,” Ferris said. “The ovaries should be evaluated with ultrasound and hormone testing, to determine if that mare has a tumor on her ovary.

“We can pull blood to check for progesterone, testosterone, inhibin, etc. There’s also a test to check for AMH (anti-mullerian hormone); if this hormone is at a certain level we would suspect the mare has a granulosa theca cell tumor.”

Various tests can be used in combination to determine if this is the problem.

“If a tumor is detected, removal of that ovary will stop the behavior,” Ferris said.

The owner may opt to have both ovaries removed, depending on whether there are future plans to breed her. If racing will be her only career, the owner might elect to have the second ovary taken out as well.

If you want foals, a mare can have normal reproduction with just one ovary. It takes a few months, however, for the second ovary to recover from effects of the abnormal hormones produced by the tumor.

“Usually, a mare won’t start cycling again for at least six to nine months, following removal of a granulosa cell tumor,” Ferris said.

“If the tumor has been there very long, the good ovary will be small and non-functional,” Sheerin said. “Removing the ovary with the tumor will allow the remaining ovary to return to functionality. The tumor secretes inhibin, suppressing the hormones of the normal ovary. If it’s been going on awhile it will take a while for the ovary to return to function.” t

Other medical problems may cause behavior mistaken for heat. A urinary tract/bladder infection might cause frequent urination, due to discomfort and irritation. Appropriate antibiotics would be necessary to resolve the infection. It is important to have a thorough examination, including vaginal inspection.

“Mares with a urinary tract infection may have an inflamed vagina, as will mares that are windsuckers,” Sheerin said. “This may cause them to posture and urinate frequently.”

Mares that pool urine in the vagina or uterus will do the same thing, because the vagina is inflamed.

“Checking with a vaginal speculum can help rule these problems in or out, along with looking at perineal conformation— whether the vulva is normal [relative to the anus] with a good seal to the lips.”

A mare with poor vulva conformation may aspirate air (windsucking) and if the anus is tipped forward there may be fecal contamination falling into the vulva.

“A mare with a uterine infection may short-cycle, instead of having a regular 21-day cycle,” Sheerin explains. “The uterus is inflamed, and releases prostaglandin; these mares may release enough to come into heat more frequently.”

Some mares occasionally have painful ovulation and show colic symptoms.

“They may do it repeatedly, or just now and then,” Sheerin said. “A mare might have a painful ovary at the beginning of breeding season and then be fine. Another mare might have this painful condition in the middle of the breeding season and then do okay. It helps to keep track of when it occurs, to figure it out. Not all mares that colic are examined via rectal palpation so it may be hard to link the two things [painful ovulation and colic] if the mare is simply treated for colic and her ovaries are not examined.”

Colic medication will generally ease pain in the ovary, but if she colics again in 3 weeks you might suspect the cause.

There are several methods for halting estrus behavior. The classic one is daily oral administration of altrenogest, a progestin (such as Regumate or a generic product).

“If an owner or trainer is wondering if behavior is associated with estrus, I often recommend a 30-day trial of Regumate, to see if that behavior ceases,” Ferris said. “If it doesn’t take away the behavior, it’s probably not associated with the estrus cycle.

Using Regumate is an inexpensive, easy way to make a diagnosis in these mares, to know if the behavior is truly estrus-related.”

Other options include injectable progesterone products.

“To inhibit estrus signs you’d give the injection daily or weekly, depending on the formulation. The downside, as with any injection given repeatedly, is that some mares might develop soreness at the injection sites. This could inhibit performance or the ability to train, so these medications are not routinely recommended,” Ferris said.

“Other synthetic progestins besides altrenogest have been tried in horses. The one most commonly used is Depo Provara. A study at CSU showed that it does not stop mares from cycling and they show signs of estrus behavior to a stallion. Progesterone and progestins do have a calming effect, however, and even though Depo Provara doesn’t stop mares from cycling [like altrenogest will], a calming effect in some mares may alter behavior enough to be more tolerable,” Ferris says. Another option is putting a glass marble into the mare’s uterus.

“About 40% of those mares will be kept out of heat for about two to three months. The idea is that the uterus thinks the mare is pregnant, which causes her to maintain her CL (corpus luteum) which would continue to secrete progesterone for 60 to 90 days. After that she would generally come into heat again, but with the marble still in place she would reform another CL.”

The drawback to this method is that it only seems to work in about 40% of mares.

“Also, a small percentage of mares have experienced major long-term ramifications after having marbles in their uterus for several years [such as breaking of the marble or chronic uterine fluid accumulation], negatively affecting their ability to become broodmares later,” Ferris said. “Another drawback is that some mares eject the marbles; they don’t stay in the uterus long enough to keep them out of heat. Inserting marbles was popular some years ago, but no longer used very much.”

Another option is to administer oxytocin by intramuscular injection. One method is to give the mare 60 units (3 ml) of oxytocin once a day, starting day seven after ovulation and continuing until the day 14 post-ovulation (about a week).

The oxytocin induces a persistent CL (and the mare continues producing her own progesterone), for about 60 to 90 days.

The downside is that you have to determine when she ovulates, to know when to start daily injections.

“This research was followed up with a second study, in which mares were given the same treatment—three ml oxytocin—but for 29 days in a row,” Ferris said. “This worked just as well and you don’t have to pinpoint the time of ovulation; you can start the mare on this protocol at any time. About 80% of mares will maintain their CL for 60 to 90 days. The nice thing about this program is there are no adverse side effects, and it is easily reversible.

“One issue with the oxytocin is that the mare’s CL has a life span of 60 to 90 days and we can’t predict exactly how long it will

last,” explains Ferris.

This is a good method to keep the mare out of heat, however, without having to give her Regumate all summer and fall.

Some horse owners prefer to not give Regumate continually, since it has health risks for both men and women if accidentally spilled on the skin. It is readily absorbed, and may cause disruption of the menstrual cycle or a miscarriage in women, and may also have adverse effect on men.

Ferris suggests discussing estrus problems with a veterinarian, to go through all the treatment options and try to figure out which one might be best for the individual mare. TFH