The Modern Equine Vet May 2019

The Modern

Equine Vet www.modernequinevet.com

Vol 9 Issue 5 2019

Running Out Of Enamel?

Post-Partum Colic: Is the Microbiome to Blame?

Preventing Sycamore Toxicity A Spoonful of Honey Heals the Wound

Intraoral

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Imaging the Possibilities

TABLE OF CONTENTS

COVER STORY

4 Finite Teeth: Caring for a

Horse That’s Running Out of Enamel Cover photo: Shutterstock/igorstevanovic

COLIC

Post-Partum Colic: Are Microbiome Changes to Blame?.............................................10 WOUND CARE

A Spoonful of Honey Heals the Wound....................................12 NEWS

AVMA Urges Congress to Act on Soring Abuses.......................... 8 Modern Equine Vet & Purina Team Up to Answer Your Nutrition Questions.................................................... 8 More on Preventing Sycamore Toxicity.......................................13 Did Horses Once Have Toes?.............................................................14 ADVERTISERS Heska..............................................................................2 Merck Animal Health..................................................5 Standlee Premium Western Forage.........................7

American Regent Animal Health.............................9 Stokes Pharmacy........................................................11

The Modern

Equine Vet SALES: Matthew Todd • Lillie Collett 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

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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DENTISTRY

F I N I T E

T E E T H :

Shutterstock/igorstevanovic

Caring for a Horse That’s Running Out of Enamel If you are treating an older horse, chances are there’s something going on in its mouth.

“We have to remember that the amount of tooth that a horse has is finite,” said Apryle A. Horbal, VMD, MPhil, MRCVS, of University Veterinary Specialists in McMurray, Pa. “As they get into their later years, we have to be focused on preserving their remaining dental tissue and providing their teeth as long a life as possible.”

Dental disease is present in an estimated 88% of horses older than 20 years of age, and that disease is often concurrent with other unrelated conditions such as degenerative joint disease (DJD) or pituitary pars intermedia dysfunction (PPID).

Maintaining normal mastication and comfort while preserving as much of the tooth as possible is crucial, Dr. Horbal said.

“We need to avoid over floating and overcorrection,” she added. “Every 2 to 3 millimeters of tooth we remove is essentially taking away 1 year of that tooth’s life.”

Equine Odontoclastic Tooth Resorption and Hypercementosis (EOTRH)

EOTRH is a resorptive dental disease that affects the incisors and canines of older horses. The roots of affected teeth begin to resorb—likely due to

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DENTISTRY

Thinking Outside the Mouth A thorough clinical evaluation prior to a dental evaluation is necessary to get the full picture.

“Auscultation of the heart can determine whether I’m anticipating any issues with sedation, such as murmurs or arrhythmias,” said Apryle A. Horbal, VMD, MPhil, MRCVS. She also evaluates the horse for clinical signs of degenerative joint disease or pituitary pars intermedia dysfunction.

She recommends running blood chemistries to diagnose any issues and "try to get them under control before I perform any significant procedures.”

“In horses with PPID—especially if it is uncontrolled—there’s delayed healing and higher rates of complication. I also determine whether a horse has arthritis, laminitis, or another condition that that may prevent them from standing for long periods or make them imbalanced.” an immune or inflammatory response—in a manner similar to the teeth of cats and humans. Signs are typically noticed by the owner at first, and include: • Disinterest in grazing, grain, pelleted feeds and treats, such as carrots and apples • Returning to wait at the gate shortly after being turned out • Picking up hay and forage with the lips only • Holding the incisors apart and/or using the tongue as a cushion between the incisors.

“There is a question as to whether we’re overdiagnosing it,” Dr. Horbal said. “It’s a common problem, and I think we’re just finding it now that we’re looking for it.”

Currently, extraction is the only recognized treatment for EOTRH when the teeth become unstable or the horse shows signs of pain.

If the resorption outpaces the hypercementosis, then the condition will be particularly painful.

Complete incisor and/or ca6

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nine extractions performed while standing in a single procedure appear to offer immediate efficacy and the least amount of stress for the horse.

“Most practitioners who do mainly dentistry perform all of the extractions while the horse is standing, but several have started doing it under general anesthesia,” Dr. Horbal said.

It is important to factor in the horse’s ability to get up after anesthesia in cases of severe DJD or other limb problems. Many practitioners also suture the sites after extraction, with the knowledge that dehiscence will occur.

“Others don’t suture, and the horses heal just fine,” she added.

“The only thing they can’t handle is short grass. Otherwise, they do fine and the owners are thrilled.”

Infundibular Disease and the Cheek Teeth

Dr. Horbal noted that most dental issues in older horses will involve the cheek teeth, since the horse essentially runs out of tooth around 20 or 30 years of age, depending on how fast the teeth erupt and the length of the crowns when they do erupt.

“Much of this has to do with the infundibulum—the cup-shaped invaginations from the occlusal surface,” she explained. “The enamel of the infundibulae is often shorter than the peripheral enamel fold, so you often end up with a tooth that has an excavated infundibulum that no longer has enamel content.”

When teeth completely run out of enamel, there are often cemental root remnants left in the mouth, which allows the opposing teeth to overgrow. This can lead to severe ulceration in the unprotected gingiva.

“That’s the balance to be aware of when you’re looking at these teeth,” Dr. Horbal said. “Look for

which teeth still have enamel and which ones have enamel that has completely worn out. Be aware of how that is going to affect the eruption and wear of those teeth.”

Periodontal Disease

While primary periodontal disease is rare in horses, periodontal disease in equine cheek teeth secondary to and associated with diastemata in the interproximal spaces is fairly common.

“We qualify diastemata as primary, secondary or senile,” Dr. Horbal said. “Senile diastemata are the least likely to resolve and the most likely to require repeat treatment.”

Radiography is important to establish the best treatment options, including options like a conservative approach, a widening approach or extraction.

“We have to be cautious when talking about extracting these teeth in older horses,” she said.

“Older horses tend to have a lot of cemental deposits around the tooth roots as they try to hold on to the teeth for as long as they can.

When you have deep periodontal pockets and the potential for fistula formation, you may start to extract old teeth with cemental deposits and you’ll look up and see a hole into the sinus or nasal cavity.

If that tooth is not mobile, you may want to think about debriding and filling that gap, and permanently occluding the diastemata.”

Dr. Horbal also stressed that all of these conditions can be painful.

“When you sedate the horse and use your NSAIDs and nerve blocks, sometimes the horse won’t stand still because it is so ramped up,” she added. “Make sure you get them into as deep of a plane of sedation as possible before treatment.”

Dr. Horbal spoke at the 64th Annual AAEP Convention in San Francisco.

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DENTISTRY

AVMA Urges Congress to Act on Soring Abuses The American Veterinary Medical Association (AVMA) asked Congress to pass the U.S. Senator Joseph D. Tydings Memorial Prevent All Soring Tactics (PAST) Act (H.R. 693), which would help eliminate the cruel and inhumane practice of soring horses.

The PAST Act would ensure that inspectors are independent and licensed by the USDA, with preference given to veterinarians, and increase penalties for violation. It would also institute a common-sense ban on action devices.

Soring is the act of deliberately causing a horse pain to exaggerate its gait. It is pervasive in the Tennessee Walking Horse industry, even though transporting or showing a sored horse is illegal.

“From a veterinary viewpoint, it's indisputable that soring causes horses an unacceptable and unnecessary level of pain,” said AVMA President John de Jong, DVM. “Unfortunately, soring practitioners have become experts at hiding evidence and even working with horse show inspectors to avoid detection. The PAST Act would provide the Department of Agriculture with the resources and enforcement mechanisms necessary to finally end

The PAST Act would

this cruel and inhumane practice.”

Soring methods include the long-term application of harsh chemicals to horses’ legs, the grinding of horses’ soles to expose sensitive tissues, the insertion of hard objects such as nails between horses’ shoes or pads and their soles, and the use of chains or other “action devices” that hide and worsen the effects of soring.

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ensure that inspectors are independent and

licensed by the USDA.

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A horse’s diet is the basis for a well-functioning body. Food is the source of energy for the horse and directly affects every stage in the horse’s life. A healthy diet is important to prevent some diseases, maintain a healthy weight and help the animal enjoy a good long life.

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But the nutritional needs of each horse differ depending on age and work, among other factors. So what would you recommend?

Get your questions answered in our new column on horse nutrition, sponsored by Purina. E-mail your questions to Marie Rosenthal, Editor. And watch for answers beginning in June.

Shutterstock/kaband

Modern Equine Vet & Purina Team Up to Answer Your Nutrition Questions

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Restore synovial joint lubrication Repair joint cartilage Reverse the disease cycle Reduce inflammation When you start with it early and stay with it as needed, horses may enjoy greater mobility 2, 4, 5 over a lifetime. Discover if Adequan is the right choice. Talk to your American Regent Animal Health sales representative or call (800) 458-0163 to order.

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3 Burba DJ, Collier MA, DeBault LE, Hanson-Painton O, Thompson HC, Holder CL: In vivo kinetic study on uptake and distribution of intramuscular tritium-labeled polysulfated glycosaminoglycan in equine body fluid compartments and articular cartilage in an osteochondral defect model. J Equine Vet Sci 1993; 13: 696-703.

4 Kim DY, Taylor HW, Moore RM, Paulsen DB, Cho DY. Articular chondrocyte apoptosis in equine osteoarthritis. The Veterinary Journal 2003; 166: 52-57.

5 McIlwraith CW, Frisbie DD, Kawcak CE, van Weeren PR. Joint Disease in the Horse.St. Louis, MO: Elsevier, 2016; 33-48.

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COLIC

Post-Partum Colic:

Are Microbiome Changes to Blame?

B y

Shutterstock/pfluegler-photo

Colic is a particular prob-

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lem for mares after foaling, and can even be fatal for animals that develop colonic volvulus. One emerging area of research has been looking at changes in the microbiome for clues about why some horses develop gastrointestinal distress after pregnancy.

In a new study, equine veterinarians in the United Kingdom found that the fecal microbiome of mares pre- and post-foaling does not appear to change significantly, suggesting that labor does not seem to alter the microbiota in ways that might trigger colic. However, the researchers also found that at least 3 easily detected compounds produced by gut bacteria did increase after delivery, which could provide a simple test for alterations in the fecal microbiome

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A d a m

should those changes prove clinically meaningful.

“VOCs are much cheaper and simpler to analyze, and this study demonstrates that they correlate well with the much more expensive and complex microbiome work, making larger studies of the gut bacteria— and the chemicals they produce— more feasible,” said Debbie Archer, BVMS, PhD, a professor in equine surgery at the Institute of Infection

M a r c u s

& Global Health at the University of Liverpool in England—who led the study. “Veterinary research does not have the large sums of money available to human researchers so this opens up important, larger-scale studies of horse gut bacteria and their relationship with certain types of colic.”

For the study, researchers used DNA analysis to track the microbial makeup of the feces of 5 pregnant mares over a period of rough-

ly 3 weeks before they foaled to about 7 weeks after delivery. They also collected samples of volatile organic compounds (VOCs) from the feces using a technique called headspace solid phase microextraction gas chromatography mass spectrometry.

The microbiomes of the mares generally remained stable across the study period, according to the researchers, although the mix of bacteria varied somewhat between animals. The researchers also identified 98 unique VOCs, but again, the prevalence of these substances didn’t vary significantly between mares or over time. However, the

concentrations of 3 VOCs—decane, 2-pentylfuran, and oct-2ene—did increase throughout the study period.

“We did not know if the VOCs would mirror the relatively stable gut microbial population so it was interesting to see that they did and that the changes in the VOCs, even with changes in stabling and turnout at grass, were relatively stable,” Dr. Archer said. “Similar to other studies done by us and other researchers, the individual horse was the most important factor that accounted for differences in the gut microbial populations and the VOCs they produce.”

For the moment, translating the research into veterinary care is complicated. “At present, VOCs are measured in a laboratory so samples could be collected from horses but vets would have to send them to a suitable laboratory,” Dr. Archer told Modern Equine Vet. “In the future, however, the aim would be to develop some form of stable-side test that detects particular VOCs. This could allow owners and vets to monitor horses at greater risk of certain types of colic for changes in VOCs to enable preventive strategies, such as dietary and other management changes, to be taken.”

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For more information: Salem SS, Hough R, Probert C, et al. A longitudinal study of the faecal microbiome and metabolome of periparturient mares. Peer J 2019;7:e6687. Published online 2019 Apr 3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6451438/

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WOUND CARE

A Spoonful of Honey

Photos courtesy of Dr. Gal Kelmer

Intralesional application of Medical grade honey (MGH) to lacerations prior to wound closure may help prevent wound infection and therefore dehiscence.

The researchers wanted to evaluate the effect of intralesional medical grade honey on wound infection and dehiscence following closure.

A total of 127 horses were included in the prospective clinical study. They were allocated random-

Various stages of healing with a wound treated with medical grade honey.

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ly into the treatment (69 horses) or control (58 horses) group. Neonatal foals, horses with major systemic illness, penetrating wounds requiring hospitalization and eyelid lacerations were excluded from the study.

All wounds were first cleaned thoroughly with diluted chlorhexidine or diluted povidone iodine followed by a balanced sterile electrolyte solution.

The medical grade honey group had sterile MGH (L-Mesitran gel) applied directly onto the subcutaneous tissue prior to skin closure or after partial wound closure. Data relating to wound healing was subsequently collected from the 11 participating practitioners through questionnaires and telephone conversations.

The honey-treated horses were significantly more likely to heal

Shutterstock/xpixel

HEALS THE WOUND

Various stages of healing with a wound treated with medical grade honey.

completely, to have no signs of infection and for the veterinarians to report some degree of satisfaction compared with control cases, according to Gal Kelmer, DVM,

MS, DACVS, DECVS, a clinical lecturer in the Department of Equine Medicine and Surgery, at the Hebrew University, Jerusalem. He told the Modern Equine

Vet he was surprised how well the honey-treated wounds healed.

No adverse effects of the honey were recorded in any of the horses participating in the study.

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For more information: Mandel HH, Sutton GA, Abu E et al. Intralesional application of medical grade honey improves healing of surgically treated lacerations in horses. Equine Vet J. 2019 Mar 21 (Epub ahead of print). https://onlinelibrary.wiley.com/doi/10.1111/evj.13111

Shutterstock/grahamspics

More on Preventing Sycamore Toxicity Neither mowing nor herbicidal spraying reduces hypoglycin A (HGA) concentration in sycamore seedlings up to 2 weeks after intervention, new research found.

Pastures contaminated with sycamore material should not be used to produce processed hay or silage. The researchers investigated various pasture management strategies employed to avoid HGA intoxication in horses.

Sycamore seedlings from 9 U.K. locations were either mowed (n = 6) or sprayed with a herbicide (dimethylamine-based n = 2; picolinic acid-based n = 1). Seedlings were analyzed for HGA concentration before intervention and at 48 hours, 1 week and 2 weeks after. Cut grass in the vicinity of mowed seedlings was also analyzed prior to and 1 week after intervention. Seeds and seedlings maintained for 6 months in processed grass forage (hay and silage) were also analyzed.

There was no significant decline in HGA content in mowed or sprayed seedlings; with mowing inducing a temporary significant rise in HGA in the seedlings. HGA was still present in sycamore material after 6–8 months storage within either hay or silage.

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For more information: GonzĂĄlez-Medina S, Montesso F, Chang Y-M, et al. Atypical myopathy-associated hypoglycin A toxin remains in sycamore seedlings despite mowing, herbicidal spraying or storage in hay and silage. Equine Vet J. 2019 Jan 10 (Epub ahead of print). https://onlinelibrary.wiley.com/doi/10.1111/evj.13070

ModernEquineVet.com | Issue 5/2019

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Photo courtesy of Eylese Rowley

NEWS NOTES

© Mark / Fotolia

Did Horses Once Have Toes?

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Palaeobiologists from the University of Bristol in the United Kingdom and Howard University in Washington, DC, have uncovered new evidence that suggests that horses' legs have adapted over time to be optimized for endurance travel, rather than speed.

The ancestors of horses, including asses and zebras, had 3 toes on each foot. Because only singletoed (monodactyl) forms survive today this anatomy has been perceived as a superior evolutionary outcome, enabling horses to outrun predators.

But the interpretation of equine evolution may be biased by human history with horses: performance at the racetrack has been less important for human history than the endurance of horses at slower speeds, and such endurance may have been the critical factor in horse evolution.

The research team combined evidence from the fossil record with existing studies on horse locomotion and propose that the adaptive significance of single-toed limbs was for trotting during roaming for food and water, rather than for galloping to avoid carnivores.

The real evolutionary step forward in horse foot anatomy was not the loss of additional toes, but the evolution of the spring foot.

This pogo-stick type of foot anatomy evolved in the 3-toed distant ancestors of modern horses, which sported an enlarged central toe but retained small side toes, which likely prevented the foot from overextending during extreme locomotor performance.

The spring foot enables the storage of elastic energy in the limb tendons during locomotion, and its evolution coincided with the spread of grasslands

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around 20 million years ago in North America (the original home of horse evolution).

The spring-footed horses radiated extensively and were as diverse during their time as antelopes in Africa today.

Around 11 million years ago, they also spread into Eurasia and Africa, where they eventually included forms larger than a modern horse. But only the lineage leading to modern horses—one among many— showed any tendency to reduce the number of toes.

“Early members of the single-toed horse lineage were not only losing their side toes, but the bones of the remaining central toe showed evidence of the boosting-up of the spring foot apparatus, implying that these horses were becoming more reliant on energy-efficient locomotion,” said Christine Janis, PhD, a professor at the University of Bristol’s School of Earth Sciences in the United Kingdom.

“But at the same time these horses’ backs were becoming shorter and stiffer, contraindicative of adaptation for the back-flexing, fast-galloping gait.

Rather, the preferred locomotion was more likely the medium-speed trot.”

The researchers propose that the early single-toed horses were changing their daily foraging behavior to roam more widely in search of food, promoting energy-saving adaptations in their feet.

The loss of the side toes may simply have been a consequence of upgrading the anatomy of the main, central toe, and with the boosted-up ligament system, their original function was no longer necessary.

Single-toed horses appeared in North America around 12 million years ago. Over the next few mil-

The ancestors of horses had 3 toes on each foot. Early horses might have changed their foraging behavior for food, promoting energy saving adapations in their feet.

lion years they radiated alongside 3-toed horses but remained pony-sized and were neither diverse nor numerous.

But at this time the climate in northern latitudes was becoming cooler and drier. An increase in roaming behavior would promote selection for the energy-efficient single-toed foot.

At the time, the foraging behavior of the single-toed horses would have been one adaptive strategy among an equine diversity, much as different kinds of antelope have different modes of foraging today.

But by around 5 million years ago, the cooling and drying trend became more intense worldwide; the former great diversity of 3-toed horses had dwindled, and the direct ancestor of modern horses (early species of the genus Equus) appeared. By 1 million years ago all lineages of 3-toed horses were extinct.

It is unlikely that competition was involved between the differently-adapted equines, as the Old World 3-toed horses started their decline several

million years before Equus emigrated from North America to join them 2.5 million years ago.

More likely, the climatic changes of the late Cenozoic favored the evolutionary strategy of the single-toed horses.

Ray L. Bernor, PhD, the coauthor of the paper, and a professor at Howard University's College of Medicine in Washington, D.C., notes that the single-toed horses really just got a lucky break due to changing climates.

“The 3-toed horses, especially the Old World hipparions, were an incredibly successful radiation, and their skeletons showed adaptations for leaping and springing as well as running. But they evolved for a world that was warmer and wetter than that of today—and like many other large mammals—did not survive to the present day,” he said.

Single-toed horses became the dominant equines across the world in the past couple of million years, and only went extinct in the Americas at the end of the Pleistocene, around 12,000 years ago.

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For more information: Janis CM, Bernor RL. The evolution of equid monodactyly: A review including a new hypothesis. Front Ecol Evol. 2019 Apr 12. DOI: 10.3389/fevo.2019.00119. https://www.frontiersin.org/articles/10.3389/fevo.2019.00119/full ModernEquineVet.com | Issue 5/2019

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