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The Modern

Equine Vet www.modernequinevet.com

Vol 10 Issue 11 2020

Cutting Your (Reproductive) Losses Stop Horsing Around With Sodium Bicarbonate Does Cryotherapy Actually Help Pain? UC Davis Finds Gene Linked to Fatal EFIH Don't Blame Dark Ronald XX

Check Out: Using Serum Amyloid A Protein Testing


TABLE OF CONTENTS

COVER STORY

4 Managing Placentitis, a Leading Cause of Reproductive Loss Cover: Shutterstock/vprotastchik

ASK THE NUTRITIONIST

Questions About Equine Nutrition? Where to Find Answers............................................. 3 SERUM AMYLOID A

Detect and Monitor Equine Inflammation Due To Infection in 10 Minutes ............... 7 SPORTS MEDICINE

For Racehorses, Hold the ‘Milkshakes’.....................................................................................10 LAMENESS

Cryotherapy: Analgesia or Just Anti-Inflammatory?.........................................................14 GENETICS

Gene Linked to Fatal EFIH Identified in Thoroughbreds...................................................16 Mystery About History of Genetic Disease in Horses..........................................................18 Common Beliefs About Arabian Horses Questioned..........................................................20 NEWS

Genetic Testing for PSSM2 .........................................................................................................13 UC Davis: Animal MASH Unit for Fire Response ..................................................................13 Many Horses With Arrhythmias Return to Racing .............................................................21 ADVERTISERS Purina Sponsored Content.................................................................................3 Merck Animal Health..........................................................................................5 Zoetis Sponsored Content..................................................................................7 American Regent Animal Health/Adequan...................................................9 American Regent Animal Health/BetaVet...................................................11

Zoetis/iSTAT.........................................................................................................13 Zoetis/Stablelab.................................................................................................15 Epicur Pharma....................................................................................................17 AVMA PLIT............................................................................................................19

The Modern

Equine Vet SALES: Matthew Todd • Matthew Gerald EDITOR: Marie Rosenthal ART DIRECTOR: Jennifer Barlow CONTRIBUTING WRITERS: Paul Basillo • Adam Marcus COPY EDITOR: Patty Wall Published by PO Box 935 • Morrisville, PA 19067 Marie Rosenthal and Jennifer Barlow, Publishers PERCYBO media  publishing

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Issue 11/2020 | ModernEquineVet.com

LEGAL DISCLAIMER: The content in this digital issue is for general informational purposes only. PercyBo Publishing Media LLC makes no representations or warranties of any kind about the completeness, accuracy, timeliness, reliability or suitability of any of the information, including content or advertisements, contained in any of its digital content and expressly disclaims liability of any errors or omissions that may be presented within its content. PercyBo Publishing Media LLC reserves the right to alter or correct any content without any obligations. Furthermore, PercyBo disclaims any and all liability for any direct, indirect, or other damages arising from the use or misuse of the information presented in its digital content. The views expressed in its digital content are those of sources and authors and do not necessarily reflect the opinion or policy of PercyBo. The content is for veterinary professionals. ALL RIGHTS RESERVED. Reproduction in whole or in part without permission is prohibited.


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Ask the

Nutritionist KELLY VINEYARD, MS, PHD, SENIOR EQUINE NUTRITIONIST, PURINA ANIMAL NUTRITION

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Ask the Nutritionist is a monthly column featuring questions answered by PhD equine nutritionists and sponsored by Purina Animal Nutrition. Have a nutrition question you want to see featured? Email Marie Rosenthal. For clinics looking for specific nutritional advice, visit purinamills.com/ask-an-expert.

Where can I find good, science-based information to refer to when I have questions related to equine nutrition? Many helpful equine nutrition resources are available for equine veterinarians, including textbooks, scientific publications, reputable websites and personal consultation with an experienced and credentialled equine nutritionist. The challenge can be ensuring the information is from a reputable source. Though not a comprehensive list, some top, science-based equine nutrition resources for equine veterinarians are highlighted below. TEXTBOOKS •  The National Academy of Sciences National Research Council’s text “Nutrient Requirements of Horses, 6th Edition”, also referred to as the “NRC,” is a key equine nutrition text. Last published in 2007, it contains scientific research in equine nutrition until that time. This text focuses on the studies that led to current established nutrient requirements for horses, and it is a “musthave” reference for equine nutrition scientists. • The textbook “Equine Applied and Clinical Nutrition” published in 2013 contains in-depth equine nutrition information from experts in the field on topics ranging from basic nutrition principles to life stage feeding to applied and clinical nutrition principles. It is an excellent reference for practitioners looking to deepen their understanding of equine nutrition and for guidance on the practical application of these nutrition principles. SCIENTIFIC PUBLICATIONS • The Journal of Equine Veterinary Science (JEVS) is the official publication of the Equine Science Society (ESS), and often contains original scientific research in equine nutrition. • The Journal of Animal Science is the official journal of the American Society of Animal Science, and journal articles cover a wide range of topics in all animal species, including equine nutrition. • Other scientific journals that often contain original equine nutrition research are the Journal of Animal Nutrition, Equine Veterinary Journal and the Journal of Animal Physiology and Animal Nutrition. WEBSITES • Many universities provide research-based knowledge to the public on various topics. University websites are a good place to search for technical bulletins and articles related to equine nutrition.

• The online NRC calculator available at https://nrc88.nas.edu/nrh/ is a handy tool when looking for equine nutrient requirements. The disclaimer popup is a good reminder that proper use requires some background knowledge of nutrition to effectively apply the calculator’s information. • The website EquineVetNutrition.com is a new resource specifically designed to support equine veterinary practitioners. All content has been created by Purina Animal Nutrition’s Ph.D. equine nutritionists experienced in clinical equine nutrition. Practical information, such as nutritional management of common equine conditions, how to interpret a hay analysis, enteral feeding guidelines, and more, can be found at this site.

EXPERT CONSULTATION A personal consultation with a trained equine nutritionist is often the most efficient path to developing supportive nutrition recommendations on specific cases. Finding someone with experience and credentials is critical. To find a DVM that is a Board-Certified Veterinary Nutritionist, consult the American College of Veterinary Nutrition’s website directory. Universities with equine extension programs often have a Ph.D. nutritionist available to answer questions as well. Independent equine nutrition consultants can be found online (confirm credentials, ask for references), and reputable feed manufacturers with Ph.D. nutritionists on staff typically offer complimentary consultations. Consultation with an experienced equine nutritionist will allow for all variables to be considered and will result in a timely and customized recommendation specific to your needs. Contact a Purina Ph.D. nutritionist for consultations through Purina Customer Service, 800-227-8941or visit EquineVetNutrition.com to submit your question.

NEED COUPONS FOR CLIENTS? You can request valuable Purina feed coupons to share with your clients at the new www.EquineVetNutrition.com page. Have a question you want to see featured? Please send them to modernequinevet@gmail.com.

ABOUT THE AUTHOR Kelly Vineyard, Ph.D., is a senior equine nutritionist with Purina Animal Nutrition. She is a frequent publisher and lecturer on equine nutrition topics, with expertise in omega-3 fatty acids, immune function and performance horse nutrition. SPONSORED BY PURINA ANIMAL NUTRITION

ModernEquineVet.com | Issue 11/2020

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REPRODUCTION

Managing Placentitis, Shutterstock/Marie Charouzova

a Leading Cause of Reproductive Loss

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Placentitis, which can affect up to 5% of broodmares in the United States, is a leading cause of reproductive loss. Most cases are caused by bacteria ascending through the cervix where they enter the choriallantois and colonize the cervical star region, releasing pro-inflammatory cytokines and prostaglandins and causing placental separation and delivery of a stillborn or weak foal. “This carries a huge economic burden in the form of loss of foal crop annually and sales at the year-

Issue 11/2020 | ModernEquineVet.com

ling sale every year,” said Jennifer L. Sones, DVM, PhD, DACT, an assistant professor of theriogenology at Louisiana State University, School of Veterinary Medicine. Management can be complex, and is expensive, she added. Both mares and any surviving foals often require intensive care. Some mares also experience repeated fertility issues the following year. “There's still a lot, we don't know about equine placentitis,” she said at the AVMA Virtual Convention 2020.


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REPRODUCTION

Ultrasonography is a useful tool—a transabdominal ultrasound can help determine fetal viability and a transrectal ultrasound will help measure the combined thickness of the uterus and placenta. Bacterial causes include Streptococcus equi zooepidemicus, Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus and Nocardia species. If Candida or Aspergillus are found, they can be a secondary infection after a bacterial placentitis. Clinical signs can be mild, moderate or severe, and some mares are asymptomatic. Their temperature, pulse and respiratory rates are often within normal limits. They might have premature udder development but that can be hard to appreciate. If they have a vulvar discharge or premature lactation, you’ve caught a severe case. “We all know mares shouldn't be dripping milk until 24 to 48 hours before foaling. So if we see that at any time before 320 days, that can be alarming and it should be,” she said. When placentitis is suspected, the mare will need a thorough reproductive examination, which includes

Biomarkers for Placentitis From about day 110 until term, total estrogen assays help to confirm pregnancy and monitor fetal viability. “An interesting feature about equine pregnancy is that progestogens really go up, up, up, and then they precipitously drop 24 hours before foaling,” said Jennifer L. Sones, DVM, PhD, DACT, a theriogenologist at Louisiana State University, School of Veterinary Medicine. The entire fetal placental unit works together to produce progestational hormones, including 5-α dihydroprogesterone, a key progestogen for maintaining pregnancy. Circulating levels of 5-α DHP will eventually exceed that of progesterone. Once that happens, supplementation may not be necessary. The UC Davis Endocrinology laboratory can now distinguish 5-α DHP from progesterone, she said. Another key steroid hormone to consider when monitoring the pregnancy is estrone sulfate. Low estrogens and progestogens, especially5-α DHP may signal fetal distress. Other biomarkers to consider are: • Serum amyloid A, which is an acute-phase protein produced in response to infection or inflammatory event. Although it is not specific to placentitis, it can be combined with the reproductive exam and other tools to help make a diagnosis and to monitor the mare’s response to treatment. • Relaxin is produced by the placenta beginning on day 80 and is increased at delivery. Low levels of circulating relaxin could signal placental dysfunction. • Alpha fetoprotein has also been shown to increase in experimental model of placentitis, and may someday be a biomarker for the condition.

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a vaginal exam through a small speculum to inspect the cervix and to look for any cervical discharge. Ultrasonography is a useful tool—a transabdominal ultrasound can help check for a fetal heart rate to determine its viability and a transrectal ultrasound will help measure the combined thickness of the uterus and placenta (CTUP). CTUP should be determined just cranial to the cervix between the middle uterine artery and allantoic space. Serial measurements should be taken because the CTUP is dynamic. Dr. Sones offered a few suggestions to make it easier to determine CTUP: • always evaluate the same area and take several measurements; • watch for features that can increase the measurement, such as physiologic edema and the amnion, and •m  easure when the foal is calm. “The foal sometimes can be very active,” she said, which can compress some of the structures together and change the measurement. “You want to do it when the foal is quiet. I often take this measurement first, and then do my reproductive exam, as I find that after I do the transabdominal ultrasound, the foal seems to be a lot more active.” The CTUP depends on the stage of gestation, but a rule of thumb is that it should be less than or equal to the month of gestation (in millimeters) when the measurement is taken. “Importantly, you want to assess if there's any placental separation. So that's going to occur in pretty severe cases of placentitis. When we see those bacteria colonize the cervical star region, and they create an inflammatory response, and they produce pus, then that mediates that placental separation. That means the placenta is not working efficiently for nutrient-oxygen exchange at those areas,” she said. Treatment goals for ascending placentitis include inhibiting and eliminating bacterial growth within the choriallantois, maintaining uterine quiescence, minimizing uterine contractions, increasing cervical tone and increasing the blood supply to the uterus and placenta.


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Use Stablelab® to measure Serum Amyloid A, a reliable biomarker for infection in horses

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quine influenza virus (EIV) outbreaks can be frightening for how quickly it can spread in horses. Imagine being at a horse show or at a barn where a few horses come down with fevers of 102°-105° F and nasal discharge. You suspect EIV. But how can you know for sure? And how can you quickly identify inflammation due to infection? This was the position Holly Helbig, DVM and owner of the Hawthorne Veterinary Clinic, found herself in while caring for horses at a show. She suspected EIV due to the signs presented, and knew she needed to act quickly to protect the other horses. “Once a case of EIV is confirmed, horse owners worry that their horses could have been exposed or possibly infected,” Helbig said. “Horse owners are looking for a quick response for peace of mind. That is where SAA testing with Stablelab comes in.” Detecting Inflammation Due To Infection With SAA Serum Amyloid A (SAA) is a major, acute phase protein produced by the liver that is a reliable biomarker for inflammation due to infection. SAA levels rapidly and dramatically increase in response to an infection.1 Using Stablelab®, a handheld stall-side diagnostic blood test, Helbig and her team conducted SAA tests on a large population of horses at the show. In 10 minutes, Stablelab detected inflammation due to possible infection in some of the horses before they showed clinical signs such as a fever. “At a show, I will have upwards of 700 horses under my care, so the SAA testing provided crucial information to help guide me in determining what horses needed to be isolated,” Helbig said. Monitoring Equine Influenza With SAA Dr. Helbig developed and quickly implemented a plan of action to isolate and care for possible infected horses. SAA testing with Stablelab

provided the results needed to successfully enforce the plan, which included: • Monitoring horses in different barns that potentially came into contact with an infected horse at the show. • Conducting an SAA test on horses showing EIV signs and obtaining results without leaving the horse’s side. • Isolating horses with SAA levels greater than 50 and then testing for EIV. • Quarantining EIV-positive horses to minimize the risk of spreading EIV. • Conducting follow-up SAA tests three days later to monitor treatment response. “In my practice, I use Stablelab primarily for a fever of unknown origin, cellulitis and respiratory issues when I am at horse shows. In cases like this one, where I suspected EIV, Stablelab proved itself a valuable tool to help me to monitor, isolate and treat infected horses,” Helbig said.

INCORPORATE STABLELAB INTO YOUR PRACTICE

The ability to identify inflammation in infected horses before they show clinical signs is critical, not only for the health of the horse, but for your clients’ peace of mind. Here are opportunities to incorporate SAA testing with Stablelab in your practice: • Primary and ambulatory care: Stablelab was designed to be used in the field to provide results in 10 minutes without leaving the horse’s side. Anytime you use antibiotics, test their SAA levels, quantify the inflammation due to infection and then use Stablelab to monitor the response to treatment. • Reproduction: Pregnancy, parturition and the early neonatal period are high-risk life stages for the horse. Conduct SAA testing to identify inflammation and ward off potential health challenges. • Referral hospital: Measure SAA as part of your minimum database at the time of admission. Screen for subclinical inflammation due to infection prior to surgery and monitor the response to treatment over their hospitalization.

LEARN MORE about testing SAA with Stablelab by talking with your Zoetis representative or visit Stablelab.com. REFERENCE 1 Jacobsen, Stine. Review of equine Acute-Phase proteins. AAEP Proceedings vol 53 2007. Pages 230 - 235. All trademarks are the property of Zoetis Services LLC or a related company or a licensor unless otherwise noted. Stablelab is a registered trademark of Epona Biotech Limited. © 2020 Zoetis Services LLC. All rights reserved. STB-00090

ModernEquineVet.com | Issue 11/2020

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REPRODUCTION

Nocardioform placentitis usually occurs from November to June with a peak in January and February, and seems to be tied to weather patterns.

“We want to counteract endotoxemia. So we want to block the release of those cytokines and prostaglandins, and then from the inflamed placenta in the hopes and the goal of preventing a spontaneous abortion,” she said. Because cervical exudate can be difficult to culture, most therapy is empiric. Antimicrobial options include potassium penicillin, gentamicin and trimethoprim sulfamethoxazole, because they accumulate in allantoic fluid. Altrenogest is given to promote uterine quiescence. Dr. Sones typically doubles the standard 0.044 mg/kg for placentitis. Some clinicians will taper the dose as the mares get closer to foaling. Anti-inflammatories are key to prevent the inflammatory cytokines and prostaglandins that promote uterine contractility. There are several choices, flunixin meglumine, phenylbutazone or firocoxib, her preferred choice. “Those are some nice oral options that you can use on the farm for some of these chronic cases,” Dr. Sones said. Pentoxifylline, a phosphodiesterase inhibitor or free radical scavenger, can be useful to promote blood flow to the fetal placental unit. “I personally have used it a lot and like it,” she said, adding that it is a fairly safe addition. Some practitioners use clenbuterol to help prevent myometrial contractions. “But there is not a whole lot of data showing that it's really preventing those myometrial contractions in the horse,” Dr. Sones said.

Other Causes of Placentitis

Nocardioform placentitis usually occurs from November to June with a peak in January and February. The causative pathogens, Crossiella equi and Amycolatopsis, tend to be environmental contaminants associated with a hot-and-dry fall prior to the breeding season. Researchers at the University of Kentucky traced these cases to the weather patterns in the fall. This year “we saw a significant number of nocardioform cases this past foaling season,” she said, which was preceded by a hot, dry fall. “We think this has something to do with changing 8

Issue 11/2020 | ModernEquineVet.com

the prevalence and the pathogenicity in the environment, and they just flourish in a hot, dry fall. These cases are hard to diagnose prior to abortion,” she said. Diagnostics are limited to mostly transabdominal ultrasonography but the lesions are difficult to image. There is treatment if accurately diagnosed, but mares will clear this infection spontaneously after the foal aborts, and they can be bred back normally. “We don't think of them as being at increased risk for repeat infections,” she said. Placentitis caused by leptospirosis is a biosecurity emergency for the farm. “If you have one positive mare on the farm, you need to quickly isolate that mare because she's going to shed it,” Dr. Sones said. Her urine, the aborted fetus and placental membrane will harbor the pathogen and can contaminate feed and water on the farm. “The mare may or may not have mild illness before abortion,” Dr. Sones said. Serial serology samples looking for rising titers can be diagnostic both before and after abortion. Detection of maternal antibodies, spirochetes in fetal kidney, placenta or maternal urine or a characteristic placental lesion—adenomatous allantoic hyperplasia—also can be diagnostic. “Those spirochetes can also be identified by dark-field microscopy in the mare's urine or by PCR after abortion,” she said. Treatment with procaine penicillin G or oxytetracycline may prevent fetal infection but will not eliminate shedding, “which is the main problem on big brood mare operations.” Prevention is key. The shedder must be isolated—maybe for months. Lepto EQ Innovator by Zoetis prevents Leptospira interrogans serovar Pomona and high-risk horses, including mares, should be vaccinated. “It's been shown to be safely given to pregnant mares in early, mid- and late gestation. But ideally you'd give them their initial dose and booster prior to pregnancy,” Dr. Sones said. “Often that's not possible, especially if mares are very quickly rebred on foal heat, but if you can even get 1 dose in before they get pregnant again [that would be ideal],” she said. MeV


Supporting veterinarians and their patients for over 30 years. American Regent Animal Health is a proud Educational Partner of the American Association of Equine Practitioners (AAEP). You can always count on us, the maker of Adequan® i.m. (polysulfated glycosaminoglycan), to passionately support and invest in our equine community. And we’ve pulled out all the stops at this year’s Virtual AAEP Convention and Trade Show. Don’t miss our digital experience, which offers live educational seminars, the opportunity to connect with ARAH representatives and our annual AAEP offer. We can’t wait to see you there.

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© 2020, American Regent, Inc. All trademarks are the property of American Regent, Inc. PP-AI-US-0538 12/2020


SPORTS MEDICINE

For Race Horses, Hold the ‘Milkshakes’ B y

A d a m

M a r c u s

ban them, but some trainers continue to administer sodium bicarbonate “milkshakes” to their animals in the hopes that the concoction will improve performance on the track. It doesn’t. A new study by researchers in Australia shows that administration of sodium bicarbonate—either through a nasogastric tube or as an oral paste—did not improve, and might even harm, equine performance. Although sodium bicarbonate has been touted as a performance enhancer in both people and animals for several decades, the data supporting its effectiveness are scarce. Many racing bodies forbid the use of the substance within 24 hours of an event; however, some trainers continue to give horses “milkshakes” against the rules. Although sodium bicarbonate is generally safe, nasogastric administration carries risks, such as gastrointestinal distress and damage to the throat from the tube. In some cases, animals have died after trainers inadvertently piped the solution into the lungs instead of the stomach. The new study, which appeared in the Journal of Equine Veterinary Medicine, was a systematic review and meta-analysis of previously published research. Joshua Denham, PhD, MA, of the School of Health and Biomedical Sciences, in Melbourne, and Adam Hulme, PhD, of the University of the Sunshine Coast, in Maroochydore DC, screened the scientific literature for studies of sodium bicarbonate for performance enhancement. They identified 7 that looked at the use of the substance in 74 horses that had undergone exercise trials—including treadmill tests and simulated track work. Six studies analyzed the “milkshake” and 1 an oral paste. Not only did sodium bicarbonate fail to improve

For more information: Denham J, Hulme A. A systematic review and meta-analysis on sodium bicarbonate administration and equine running performance: Is it time to stop horsing around with baking soda? J Equine Vet Sci. 95 (2020) 103281 https://www.sciencedirect.com/science/article/abs/pii/S0737080620303725 10

Issue 11/2020 | ModernEquineVet.com

performance, according to the researchers, the metaanalysis pointed to “a very small negative effect of sodium bicarbonate on running performance.” “It would be great to see vets educate others about our recent findings and for some to reconsider the use of sodium bicarbonate on race day,” Dr. Denham told Modern Equine Vet. “Why perform a stressful procedure if it does not improve exercise performance and is a banned practice on race day? We know from human athletes that psychological stress hinders performance and increases the risk of injuries.” Dr. Denham added that, “although potentially clutching at straws,” researchers might tweak future studies of sodium bicarbonate. “For instance, the use of timing gates for quantifying simulated race times rather than hand-held stop watches. They could control for other potential confounding variables such as fluid intake, anthropometrics, diets, etc., and determine whether timing or dosage plays any role. I'm not convinced it will change the results, but there are limitations that could be addressed in future work.” From his perspective, however, the results speak for themselves: “There are moral, legal and scientific reasons for not administering sodium bicarbonate to racehorses on race day.” MeV

Shutterstock/Stefan Holm

Horses might not like them, and racing bodies


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The link between RAPID ONSET and LONG-ACTING RELIEF of pain & inflammation1 BetaVet ® (betamethasone sodium phosphate & betamethasone acetate injectable suspension) is indicated for the control of pain and inflammation associated with osteoarthritis in horses. Learn more at www.betavetequine.com or call 1-800-458-0163. Please see Brief Summary of Full Prescribing Information on the following page.

INDICATION: BetaVet ® is indicated for the control of pain and inflammation associated with osteoarthritis in horses.

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CONTRAINDICATIONS: BetaVet ® is contraindicated in horses with hypersensitivity to betamethasone. Intra-articular injection of corticosteroids for local effect is contraindicated in the presence of septic arthritis. WARNINGS: Do not use in horses intended for human consumption. Clinical and experimental data have demonstrated that corticosteroids administered orally or parenterally to animals may induce the first stage of parturition when administered during the last trimester of pregnancy and may precipitate premature parturition followed by dystocia, fetal death, retained placenta, and metritis. Additionally, corticosteroids administered to dogs, rabbits and rodents during pregnancy have resulted in cleft palate in offspring and in other congenital anomalies including deformed forelegs, phocomelia and anasarca. Therefore, before use of corticosteroids in pregnant animals, the possible benefits to the pregnant animal should be weighed against potential hazards to its developing embryo or fetus. Human Warnings: Not for use in humans. For use in animals only. Keep this and all medications out of the reach of children. Consult a physician in the case of accidental human exposure. PRECAUTIONS: Corticosteroids, including BetaVet ®, administered intra-articularly are systemically absorbed. Do not use in horses with acute infections. Acute moderate to severe exacerbation of pain, further loss of joint motion, fever, or malaise within several days following intra-articular injection may indicate a septic process. Because of the anti-inflammatory action of corticosteroids, signs of infection in the treated joint may be masked. Due to the potential for exacerbation of clinical signs of laminitis,

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glucocorticoids should be used with caution in horses with a history of laminitis, or horses otherwise at a higher risk for laminitis. Use with caution in horses with chronic nephritis, equine pituitary pars intermedia dysfunction (PPID), and congestive heart failure. Concurrent use of other anti-inflammatory drugs, such as NSAIDs or other corticosteroids, should be approached with caution. Due to the potential for systemic exposure, concomitant use of NSAIDs and corticosteroids may increase the risk of gastrointestinal, renal, and other toxicity. Consider appropriate wash out times prior to administering additional NSAIDs or corticosteroids. ADVERSE REACTIONS: Adverse reactions reported during a field study of 239 horses of various breeds which had been administered either BetaVet ® (n=119) or a saline control (n=120) at five percent (5%) and above were: acute joint effusion and/or local injection site swelling (within 2 days of injection), 15% BetaVet ® and 13% saline control; increased lameness (within the first 5 days), 6.7% BetaVet ® and 8.3% saline control; loose stool, 5.9% BetaVet ® and 8.3% saline control; increased heat in joint, 2.5% BetaVet ® and 5% saline control; and depression, 5.9% BetaVet ® and 1.6% saline control. DOSAGE AND ADMINISTRATION: Shake well immediately before use. Use immediately after opening, then discard any remaining contents. RX ONLY References: 1. Trotter GW. Intra-articular corticosteroids. In: McIlwraith CW, Trotter GW, eds. Joint Disease in the Horse. Philadelphia: W.B. Saunders; 1996; 237–256.

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5/17/2019 9:15:15 AM


BRIEF SUMMARY OF PRESCRIBING INFORMATION (Betamethasone Sodium Phosphate and Betamethasone Acetate Injectable Suspension) 6 mg betamethasone per mL For Intra-Articular (I.A.) Use in Horses CAUTION: Federal law restricts this drug to use by or on the order of a licensed veterinarian. INDICATION: BetaVet® is indicated for the control of pain and inflammation associated with osteoarthritis in horses. DOSAGE AND ADMINISTRATION: Shake well immediately before use. CONTRAINDICATIONS: BetaVet® is contraindicated in horses with hypersensitivity to betamethasone. Intra-articular injection of corticosteroids for local effect is contraindicated in the presence of septic arthritis. WARNINGS: Do not use in horses intended for human consumption. Clinical and experimental data have demonstrated that corticosteroids administered orally or parenterally to animals may induce the first stage of parturition when administered during the last trimester of pregnancy and may precipitate premature parturition followed by dystocia, fetal death, retained placenta, and metritis. Additionally, corticosteroids administered to dogs, rabbits and rodents during pregnancy have resulted in cleft palate in offspring. Corticosteroids administered to dogs during pregnancy have also resulted in other congenital anomalies including deformed forelegs, phocomelia and anasarca. Therefore, before use of corticosteroids in pregnant animals, the possible benefits to the pregnant animal should be weighed against potential hazards to its developing embryo or fetus. Human Warnings: Not for use in humans. For use in animals only. Keep this and all medications out of the reach of children. Consult a physician in the case of accidental human exposure. PRECAUTIONS: Corticosteroids, including BetaVet®, administered intra-articularly are systemically absorbed. Do not use in horses with acute infections. Acute moderate to severe exacerbation of pain, further loss of joint motion, fever, or malaise within several days following intra-articular injection may indicate a septic process. Because of the anti-inflammatory action of corticosteroids, signs of infection in the treated joint may be masked. Appropriate examination of joint fluid is necessary to exclude a septic process. If a bacterial infection is present, appropriate antibacterial therapy should be instituted immediately. Additional doses of corticosteroids should not be administered until joint sepsis has been definitively ruled out. Due to the potential for exacerbation of clinical signs of laminitis, glucocorticoids should be used with caution in horses with a history of laminitis, or horses otherwise at a higher risk for laminitis. Use with caution in horses with chronic nephritis, equine pituitary pars intermedia dysfunction (PPID), and congestive heart failure. Concurrent use of other anti-inflammatory drugs, such as NSAIDs or other corticosteroids, should be approached with caution. Due to the potential for systemic exposure, concomitant use of NSAIDs and corticosteroids may increase the risk of gastrointestinal, renal, and other toxicity. Consider appropriate wash out times prior to administering additional NSAIDs or corticosteroids. ADVERSE REACTIONS: Adverse reactions reported during a field study of 239 horses of various breeds which had been administered either BetaVet® (n=119) or a saline control (n=120) were: acute joint effusion and/or local injection site swelling (within 2 days of injection), 15% BetaVet® and 13% saline control; increased lameness (within the first 5 days), 6.7% BetaVet® and 8.3% saline control; loose stool, 5.9% BetaVet® and 8.3% saline control; increased heat in joint, 2.5% BetaVet® and 5% saline control; depression, 5.9% BetaVet® and 1.6% saline control; agitation/anxiety, 4.2% BetaVet® and 2.5% saline control; delayed swelling of treated joint (5 or more days after injection), 2.5% BetaVet® and 3.3% saline control; inappetance, 3.4% BetaVet® and 2.5% saline control; dry stool, 1.7% BetaVet® and 0% saline control; excessive sweating, 0.8% BetaVet® and 0% saline control; acute non-weight bearing lameness, 0.8% BetaVet®and 0% saline control; and laminitis, 0.8% BetaVet® and 0% saline control.

CLINICAL PHARMACOLOGY: Betamethasone is a potent glucocorticoid steroid with anti-inflammatory and immunosuppressive properties. Depending upon their physico-chemical properties, drugs administered intra-articularly may enter the general circulation because the synovial joint cavity is in direct equilibrium with the surrounding blood supply. After the intra-articular administration of 9 mg BetaVet® in horses, there were quantifiable concentrations of betamethasone (above 1.0 ng/mL) in the plasma. EFFECTIVENESS: A negative control, randomized, masked field study provided data to evaluate the effectiveness of BetaVet® administered at 1.5 mL (9 mg betamethasone) once intra-articularly for the control of pain and inflammation associated with osteoarthritis in horses. Clinical success was defined as improvement in one lameness grade according to the AAEP lameness scoring system on Day 5 following treatment. The success rate for horses in the BetaVet® group was statistically significantly different (p=0.0061) than that in the saline group, with success rates of 75.73% and 52.52%, respectively (back-transformed from the logistic regression). ANIMAL SAFETY: A 3-week target animal safety (TAS) study was conducted to evaluate the safety of BetaVet® in mature, healthy horses. Treatment groups included a control (isotonic saline at a volume equivalent to the 4x group); 1X (0.0225 mg betamethasone per pound bodyweight; BetaVet®); 2X (0.045 mg betamethasone per pound bodyweight; BetaVet®) and 4X (0.09 mg betamethasone per pound bodyweight; BetaVet®). Treatments were administered by intra-articular injection into the left middle carpal joint once every 5-days for 3 treatments. Injection site reactions were the most common observations in all treatment groups. Injection site reactions were observed within 1 hour of dosing and included swelling at the injection site, lameness/stiffness of the left front limb, and flexing the left front knee at rest. The injection site reactions ranged from slight swelling (in many horses on multiple days in all treatment groups) to excessive fluid with swelling, pain, and lameness (4x group only). Injection site reactions were observed most commonly on treatment days, and generally decreased in number and severity over subsequent days. The incidence of injection site reactions increased after the second and third injection (number of abnormalities noted on day 10 > day 5 > day 0). In the BetaVet® treated groups the number and severity of the injection site reactions were dose dependent. The 4X BetaVet® group had the highest overall incidence of and severity of injection site reactions, which included heat, swelling, pain, bleeding, and holding the limb up at rest. The control group and 4X group (which received similar injection volumes) had a similar incidence of injection site reactions; however, the severity of reactions was greater in the 4X group. Absolute neutrophils were statistically significantly higher in the BetaVet® treated groups as compared to the control group. Trends toward a decrease in lymphocytes and eosinophils, and an increase in monocytes were identified in the BetaVet® treated groups after the initial dose of BetaVet®. Individual animal values for white blood cells generally remained within the reference range. BetaVet® treated horses also had a trend toward increased blood glucose after the initial dose. Some individual animals showed mild increases in blood glucose above the reference range. SHAKE WELL BEFORE USING NADA 141-418, Approved by FDA For customer care or to obtain product information visit www.betavetequine.com or call 1-800-458-0163. To report an adverse event please contact American Regent Animal Health at (800) 734-9236 or email pv@americanregent.com.

A Division of American Regent, Inc. 5 Ramsey Rd. | Shirley, NY 11967


NEWS NOTES

Genetic Testing for PSSM2 P variant alleles (P2, P3 and P4) are currently used in commercial testing for type 2 polysaccharide storage myopathy (PSSM2) and myofibrillar myopathy (MFM). A recent study compared the frequencies of these alleles between 98 Warmblood and Arabian horses diagnosed with PSSM2/MFM by muscle histopathology, and 84 matched control horses. There was no significant association between any P locus and a histopathological diagnosis of PSSM2 or MFM. The sensitivity for the P variants for predicting PSSM2/MFM was poor (<33%) for all P variants in both Warmbloods and Arabian horses. Frequencies of these P variants in modern, early

domestic and Przewalski horses were determined from a public data repository. All P variants were present in early domestic horses and P2 was also present in the Przewalski horse, suggesting that they are unlikely to confer a disadvantage to health and fitness. A careful history, physical examination, serum creatine kinase activity, PSSM1 genetic test, and, in the absence of PSSM1 results, muscle histopathology, represent more accurate and validated means to differentiate the many causes of exertional myopathies in horses. The P variants used in commercial genetic tests are not predictive of the presence or absence of PSSM2 or MFM, the researchers said. MeV

For more information: Valberg SJ, Finno CJ, Henry ML, et al. Commercial genetic testing for type 2 polysaccharide storage myopathy and myofibrillar myopathy does not correspond to a histopathological diagnosis. Equine Vet J. 2020;00:1â&#x20AC;&#x201C;11Sept 8 [Epub open access]. https://beva.onlinelibrary.wiley.com/doi/10.1111/evj.13345

UC Davis: Animal MASH Unit for Fire Response

Since August 19, the UC Davis School of Veterinary Medicine has been treating animals burned in the devastating LNU Lightning Complex Fire. Using a field-first approach, the school's Veterinary Emergency Response Team (VERT) deployed to Solano and Sonoma Counties to care for animals at evacuation centers and those sheltering in place on ranches. They also conducted search and rescue missions throughout the fire zones. Meanwhile, the veterinary hospital concentrated on only the most critical cases. This strategy has successfully allowed VERT to evaluate, triage and/or treat more than 1,000 animals in the field, while critical care specialists at the hospital care for 30 of the most severely injured animals.


LAMENESS

Cryotherapy: Analgesia or Just Anti-inflammatory? By Paul Basilio Cryotherapy’s effects on inflammation are well known in both human and veterinary medicine, but an accurate analgesic picture is still unclear. To help fill in the gaps, Vivian Quam, MA, DVM, and colleagues designed an induced-lameness model applicable to sport horses in competition. “The ultimate objective is to understand how best to utilize cryotherapy as a tool for multimodal analgesia in our patients, as well as for a tool for safely managing the sport horse in competition,” said Dr. Quam, from the Department of Veterinary Clinical Sciences at The Ohio State University. In human sports medicine, cryotherapy has been employed commonly as an alternative or complementary therapy in elite athletes that face drug screening. It decreases synovial inflammation and knee pain in nonseptic joints for more than 24 hours, and intermittent cryotherapy improves pain, function and swelling in closed soft-tissue injuries. “It has also been shown to increase the pain threshold and pain tolerance at the site of cryotherapy application as well as at distal locations,” Dr. Quam said. “This suggests that a reduction in nerve conduction velocity is the mechanism of action for the analgesic effect of cryotherapy.”

Testing the Unknown

Dr. Quam’s team hypothesized that 60 minutes of cryotherapy in an ice water slurry would produce an analgesic effect that could be observed with a noninvasive sensor in horses with an induced forelimb lameness. The researchers selected 10 mature research horses with a normal physical examination and a negligible degree of observed lameness when trotted on a straight line, and all experimental procedures were conducted in accordance with IACUC standards. Study horses were sedated with IV acepromazine. The first dose was administered prior to a 100-m baseline jog on grass, and the second dose was administered while in stocks halfway through the treatment hour. Each horse was assigned to the cryotherapy or control group during the first treatment period, and they were then crossed over following a 2-week washout. A farrier applied steel keg shoes to both forefeet. The medial and lateral shoe branches had pre-drilled holes at the level of the heel bulbs to induce an AAEP Grade 3 lameness via screw application. It should be noted that their transient lameness model was successful, in that a similar lameness level was noted before lameness induction and shortly after the study period. The affected distal forelimbs were maintained at 6° C using a cryotherapy boot filled with an ice slurry 14

Issue 11/2020 | ModernEquineVet.com

in the experimental group or at ambient temperature in the control group. The contralateral limbs in each group were outfitted with a standard gel orthotic. “After the treatment hour, the degree of lameness was assessed at 5, 10, 15, 20, 30, 45, and 60 minutes post-treatment,” Dr. Quam said. “The screw was removed and lameness was assessed following removal to ensure that the method of lameness induction was not causing excessive pressure and pain that would persist following removal.”

Results

Cryotherapy was maintained without difficulty for the duration of treatment, and no changes in heart rate that would indicate pain from treatment were seen. The degree of induced lameness did not differ between cryotherapy and control groups, indicating that lameness induction was successful and both groups had the same degree of lameness before and after induction. “Both treatment groups experienced a reduction in lameness following the treatment hour,” Dr. Quam said. “However, the cryotherapy had a statistically significant lameness improvement at 5 and 10 minutes after the treatment period, indicating that the degree of lameness was improved at these points.” In the control group, however, there was only statistical significance at 5 minutes post-treatment. No significant improvement in lameness was noted for either group 15 minutes following treatment or in subsequent assessments. At 15 minutes, the lameness improvement was greater for the cryotherapy group than for the control group. After 1 hour, the treatment group had a longer duration of improved lameness vs. controls. In addition, 1° of lameness improvement was detectable in the cryotherapy group, but only at 15 minutes of treatment. “This study showed a modest reduction in lameness following 1 hour of cryotherapy, while the therapeutic effect diminished over the post-treatment hour,” she said. “Significant lameness improvement could be detected at least 10 minutes after cryotherapy.” This work serves as groundwork for further research that should determine the ideal method, duration and temperature for provision of analgesia, she said. “We could have missed a small analgesic effect over a longer period in the study due to the small number of [horses] and high individual variability. Alternatively, the time of cryotherapy in this model may have been insufficient to maintain an optimal effect of the hypothermia.” Dr. Quam discussed her research at the AAEP 65th Annual Convention & Trade Show in Denver. MeV


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ModernEquineVet.com | Issue 11/2020

15


GENETICS

Gene Linked to Fatal EFIH

A genetic

Photo courtesy of UC Davis

cause for the fatal condition equine familial isolated hypoparathyroidism (EFIH) in Thoroughbreds was identified marking the first genetic variant for hypoparathyroidism identified in any domestic animal species. The University of California Davis, School of Veterinary Medicine, which identified the gene, also offers the first widely available genetic test for Thoroughbreds, which is performed

16

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at the UC Davis Veterinary Genetics Laboratory. Testing enables breeders to identify horses with the variant and avoid mating carriers that could produce affected foals. “For Thoroughbred owners and breeders, the loss of a foal has tremendous economic and emotional impacts,” said first author Victor Rivas, PhD, who conducted the project as part of his undergraduate training in the laboratory run by Carrie Finno, DVM, PhD, DACVIM. “It is important to promote safe and strategic breeding habits by actively breeding horses genetically screened not only for EFIH, but for other diseases that may impact quality of life.” Foals affected with EFIH suffer from low blood calcium concentrations, resulting in involuntary muscle contractions and muscle stiffness that leads to a stiff gait, which can progress to an inability to stand, seizures, fevers and an abnormally fast pulse. Parathyroid hormone is typically produced to increase calcium levels in the body, but in these foals, concentrations are low or “inappropriately” normal (i.e. they should be high due to the low calcium). Affected foals die or are euthanized due to poor prognosis. Necropsy results re-

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GENETICS

veal underdeveloped or absent parathyroid glands. Previously termed idiopathic hypocalcemia, EFIH has been observed in Thoroughbred foals up to 35 days of age. Disease onset and progression are likely determined by the amount of calcium in the diet early in life. This can vary based on dam milk calcium concentration and the amount of milk ingested. The current study determined an autosomal recessive mode of inheritance and performed whole genome sequencing of 2 affected foals. A mutation in the Rap Guanine Nucleotide Exchange Factor 5 (RAPGEF5) gene was present in 2 copies (homozygous) in both foals. The variant was further analyzed in a frog developmental model and demonstrated loss-of-function of the RAPGEF5 protein leading to aberrant development. Based on these data, the researchers hypothesize that RAPGEF5 may play a role in the derivation of the parathyroid gland during development. The variant was not identified in individuals from 12 other breeds. The allele frequency for the RAPGEF5 variant in an expanded set of 82 randomly selected, unaffected Thoroughbreds was 0.018. An unbiased allele frequency study has not been performed, so the allele

frequency in the larger Thoroughbred population is unknown. “The next steps are to assess the allele frequency in a large population of randomly selected Thoroughbreds,” Finno said. “Additionally, we have discussed collaborating with Dr. Nathan Slovis at Hagyard Equine Medical Institute in Kentucky to test for the variant in cases of ‘sudden death’ in Thoroughbred foals.” The clinical presentation of EFIH is similar to human familial hypoparathyroidism. Since the RAPGEF5 gene is highly conserved across species, it is a potential new candidate gene for primary hypoparathyroidism in humans. “This type of research discovery requires a unique collaboration among clinicians, pathologists and basic researchers,” Dr. Finno said, adding that samples were submitted from universities and laboratories across the country. Support for this study was provided by the UC Davis Center for Equine Health. MeV Click on the link for information about the UC Davis Veterinary Genetics Laboratory https://vgl.ucdavis.edu/

For more information: Rivas VN, Magdesian KG, Fagan S, et al. A nonsense variant in Rap Guanine Nucleotide Exchange Factor 5 (RAPGEF5) is associated with equine familial isolated hypoparathyroidism in Thoroughbred foals. Plos Genetics 2020[Epublished Sept. 28] https://doi.org/10.1371/journal.pgen.1009028. https://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1009028

Mystery About History of Genetic Disease in Horses Dark Ronald XX is not the father of Warmblood fragile foal syndrome.

Warmblood fragile foal syndrome is a severe, usually fatal, genetic disease that manifests itself after birth in affected horses. Due to the defect, the connective tissue is unstable. Under force, for instance, the skin tears from the tissue underneath and the joints can suffer dislocation. A research team from the Universities of Göttingen and Halle showed that the disease did not stem from the English Thoroughbred stallion Dark Ronald XX, which had been the assumption until now. The mystery of the genetic defect could have been solved in 2012: this is when the gene responsible was identified. It is called PLOD1 and normally ensures that collagen molecules in the skin and connective tissue can bind to form a stable network. The muta18

Issue 11/2020 | ModernEquineVet.com

tion in the PLOD1 gene prevents “cross-linking” which is needed for stable collagen. The exact origin of the mutation was previously unclear. Since the spread of the genetic defect is also 3.a problem in horse-breeding in Germany, the Vereinigte Informationssysteme Tierhaltung (IT-Solutions for Animal Production) previously determined the possible origin of the genetic defect from the test results of around 2,000 horses and their pedigree records. The investigation concluded that the genetic defect was probably due to the English Thoroughbred stallion Dark Ronald XX (1905-1928) or his father, Bay Ronald XX, and the defect was then spread through their offspring. The current research, led by the University of Göt-


tingen, calls this theory into question. “We have now succeeded in proving that Dark Ronald XX was not a carrier of the PLOD1 mutation and can therefore be excluded as the original source of this genetic defect,” said Prof. Bertram Brenig, PhD, director of the Institute of Veterinary Medicine at the University of Göttingen and lead author of the study. Doubts about whether the mutation descended from Dark Ronald XX were already expressed in 2019, and further investigation points to a Hanoverian stallion born in 1861. Dark Ronald XX was an important Thoroughbred stallion who had a great influence on German horsebreeding. He was sold to Germany in 1913 and was used as a stud first in Graditz and later in Altefeld. In 1928, he was brought to the veterinary clinic of the University of Halle for treatment due to intestinal colic, where he died. Since then his remains have been

kept in 1 of the natural science collections of the Martin Luther University Halle-Wittenberg. “This is most fortunate, as it has allowed us to examine Dark Ronald XX directly for the presence of the PLOD1 mutation,” Dr. Brenig said. The scientists were able to examine small pieces of Dark Ronald XX's skin. “Examining the DNA from the nearly 100-year-old skin of Dark Ronald XX was not easy,” said co-author Renate Schafberg, Dr rer nat, from the University of Halle, “because we knew nothing about the tanning or other preservation treatments of the skin.” The disease itself is not new and probably originated in the middle of the 18th century. Since then, all breeding animals have been consistently tested for the genetic defect. There is a comparable genetic disease in humans, known as Ehlers-Danlos syndrome, which shows similar symptoms. MeV

For more information: Zhang X, Hirschfeld M, Schafberg R, et al. Skin exhibits of Dark Ronald XX are homozygous wild type at the Warmblood fragile foal syndrome causative missense variant position in lysyl hydroxylase gene PLOD1. Animal Genetics 2020; DOI: 10.1111/age.12972

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GENETICS

A study involving Arabian horses from 12

countries found that some populations maintained a larger degree of genetic diversity and that the breed did not contribute genetically to the modern-day Thoroughbred, contrary to popular thought. The researchers collected and examined DNA samples from 378 Arabian horses from Qatar, Iran, United Arab Emirates Poland, United States, Egypt, Jordan, Kuwait, United Kingdom, Australia, Denmark and Canada. The research was conducted over an 8-year period, beginning in 2014. The process was a lot of effort, according to Samantha Brooks, PhD, a UF/IFAS assistant professor of animal sciences at the University of Florida, in part due to traveling to collect the Arabians' blood and hair samples, as well as natural delays in working with international colleagues to collect and ship other samples. The samples were anonymized for data analysis purposes, except to note the horse's location and categorizing them as endurance competition, flatcourse racing or show horses. The data set was also expanded using information from past studies on other breeds, which included Thoroughbreds, Per-

sian Arabian, Turkemen and Straight Egyptians. “The Arabian horse has a special mystique due to the long recorded history of the breed,” Dr. Brooks said. “Arabian horse breeders, in particular, know their horse's bloodlines many generations back. What we found was that in the area where this breed originates— likely the near East region, but we don't know exactly —there's a healthy level of diversity. This is particularly evident in populations from Bahrain and Syria, which suggests these are some pretty old populations.” The horse is prized for characteristics like heat tolerance and endurance, as well as its unique appearance, with a dish-shaped facial profile, wide-set eyes, an arched neck and a high tail carriage. It has been exported from its ancestral homeland for centuries, with some modern lineages drawn strictly from these smaller genetic pools, giving the breed a reputation for inbred disorders. While this was true for some groups they tested, Dr. Brooks noted, they also found remarkable diversity when considering the breed as a whole. Dr. Brooks contrasted the discovery of more diverse populations with the samples they received from racing Arabians. Another longstanding myth says that the Arabian contributed genetically to the modern Thoroughbred, but the racing Arabians' DNA told a different story. “What we found in these samples was not that much Arabian ancestry was part of the Thoroughbred line, but the opposite: that Thoroughbred DNA exists in most of the modern racing Arabian lines, indicating a more recent interbreeding within this group,” Dr. Brooks said. “I can't speculate on the how or why, but this is clearly the story the DNA is telling us.” Another implication of this study, Dr. Brooks said, is the potential to identify the genetic regions that determine some of the Arabian's unique traits, like their facial profile. This could be expanded to identify the marker for other horse breeds' head shapes, for example. The research was funded by a grant from the Qatar National Research Fund with additional support from the Harry M. Zweig Memorial Fund for Equine Research, Arabian Horse Foundation, Animal Health Foundation, Dorothy Russell Havemeyer Foundation, Inc. and a Meinig Family Investigator award. MeV

For more information: Cosgrove EJ, Sadeghi R, Schlamp F, et al. Genome diversity and the origin of the Arabian horse Sci Rep. 2020 Jun 16;10(1):9702. doi: 10.1038/s41598-020-66232-1.PMID: 32546689. https://www.nature.com/articles/s41598-020-66232-1 20

Issue 11/2020 | ModernEquineVet.com

Shutterstock/Olga_i

Common Beliefs About Arabian Horses Questioned


NEWS NOTES

Many Horses With Arrhythmias Return to Racing Exercise-associated rhythm disturbances are common in poorly performing Thoroughbreds, but their presence was not associated with return to racing, and a high proportion of horses raced again. This retrospective study done at the Rossdale Diagnostic Center in England examined exercising electrocardiogram recordings for 245 Thoroughbred racehorses presenting with poor performance and/ or respiratory noise at exercise. In total, 158 horses (64.5%) had abnormal rhythms; 110 (44.9%) of these had isolated premature depolarisations and 48 (19.6%) horses had complex tachydysrhythmias. Rhythm disturbances were most common during recovery from exercise (50% of horses).

Horses being exercised on a treadmill were 2.6 times more likely to have rhythm disturbances than those exercised over ground, and National Hunt racehorses were 2.7 times more likely to have complex arrhythmias than horses engaged in flat racing. Exercise-associated upper respiratory tract (URT) obstruction was associated with the presence of rhythm disturbances. Horses with URT obstruction at exercise were twice as likely to have a rhythm disturbance than those with normal airway function. Overall, 82% of horses raced again. There were no significant differences in the number of horses that returned to racing in the normal rhythm, isolated premature depolarisations or complex rhythm groups. MeV

For more information: Marr CM, Franklin S, Garrod G, et al. Exercise associated rhythm disturbances in poorly performing Thoroughbreds: Risk factors and association with racing performance. Equine Vet J. 2020 Sept. 26 [Epub ahead of print]. https://beva.onlinelibrary.wiley.com/doi/10.1111/evj.13354

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