EQUINE NEWS September 2017

Influence of Diet & Exercise on Developmental Orthopedic Disease

Effect of Diet

Many nutritional causes of developmental orthopedic diseases (DOD) have been

proposed with very few providing direct causative relationships in a research setting.

However, that may be due to a lack of combining the correct causative factors in this

multifactorial disease. Foal used in research trials may need to have a genetic

predisposition for developmental orthopedic disease, and then must be exposed to

the right management conditions to initiate the disease process. These

combinations are often hard to find in traditional equine research trials. However,

the most commonly identified factors include excess energy, mineral imbalances,

and inadequate protein. One contributing factor in the development of DOD is

feeding of excessive non-structural carbohydrates (sugars and starches) to growing

horses. These glucose rich feedstuffs (think traditional cereal grains like corn) cause

a more rapid increase in blood glucose post feeding versus feeds containing more

fiber. Higher levels of blood glucose increase insulin levels in the young horse. Insulin

initiates a cascade of metabolic events which may carry down to the level of cartilage

maturation. While it has been shown repeatedly that feeding high concentrate diets

alters the glucose/insulin response and reduces insulin sensitivity, the direct

causative relationship to developmental orthopedic diseases has not been firmly

established. The most important guideline appears to be to avoid unregulated

feeding of concentrates, especially those higher in sugars and starches. High protein

diets have also fallen under the radar of causing developmental orthopedic disease,

but this has not been able to be shown in a research setting. When considering your

protein source for your growing foal, remember to not only consider the amount, but

the quality of protein as well. Please see ANSI-3977 Managing Young Horses for

Sound Growth for more details.

Mineral nutrition has probably seen the greatest attention related to developmental

orthopedic diseases. To begin the simplest, imbalances of deficiencies of calcium

(Ca) and phosphorus (P) can clearly lead to abnormalities of bone development.

Please see ANSI 3934: Minerals for Horses: Calcium and Phosphorus. Low calcium/

phosphorus diets fed to mares and foals resulted in a greater risk of developing DODs

(Lepeule et al. 2011). However, feeding adequate amounts of Ca and P in the correct

ratios does not guarantee your foal will be free from abnormalities. Other nutrients

contribute to sound growth as well, for example. These include copper and zinc.

Copper should be fed at a concentration at 10 ppm while zinc should be included at

40 ppm in diets of the growing horse. The most promising results of supplementing

copper have been seen when providing copper to the dam in late gestation, or in

supplementing copper to promote the repair of osteochondrosis lesions.

Supplementation beyond these levels at this point is not warranted.

Genetics

Unfortunately, the genetics of your foal may be the single largest contributing factor

to developmental orthopedic disease. Heritability estimates of osteochondrosis may

even by as high as 0.52, or in other words, genetics may play 50% of the role in

development of skeletal abnormalities. Osteochondrosis may include several

different genes and loci, which may even differ by breed (Sevane et al, 2016). While

this sheds some interesting new light on the problem, it is also difficult for breeders

to select against. Compared to a single point mutation like HYPP, horses cannot be

identified as simple carriers of a specific gene for the disease. Screening for potential

carriers of OC at this point would be costly and ineffective, but may be available in

the future. However, that does not mean the breeder has little recourse. If your

mare has consistently produced foals with OCs, your management program may be

inadequate or, she may have a genetic likelihood to produce these types of foals. It

may be very important to consider both factors in future breedings. Consider the

stallion as well. You can often hear rumblings in the horse community about certain

stallions which tend to sire foals with DOD. Perhaps these are individuals we should

select against when breeding for sound foals. Hopefully the amount of research

currently being conducted on the genetic link to OCs will limit this disorder in the

future.

Taken all together, the best plan for avoiding development orthopedic disease may

be first to select genetically healthy individuals to breed. Secondly, the foal should

be managed with attention to diet and exercise up until they are two years of age.

Many causes of DOD may be unavoidable, but with proper care and management,

one can produce a healthy normal adult.

References

Lepeule, J., H. Seegers, V. Rondeau, C. Robert, J.M. Denoix and N Bareille. 2011. Risk

factors for the presence and extent of developmental orthopaedic disease in the

limbs of young horses: Insights from a count model. Preventive Veterinary Medicine.

101 (1-2):96-106.

Sevane, N. S. Dunner, A. Boado, and J. Canon. 2016. Candidate gene analysis of

osteochondrosis in Spanish purebred horses. Animal Genetics. 47(5):570-578.

Kris Hiney, PhD

Equine Extension Specialist

Oklahoma State University

The OSU Veterinary Medical Hospital has been serving horse owners since 1948. We

offer routine appointments Monday-Friday and 24 hour emergency service including

holidays. The equine medicine and surgery service is staffed by board certified

specialists, post-graduate veterinary residents, and senior veterinary students. The

service is supported by board certified specialists in other areas of the hospital

including anesthesiology, ophthalmology, radiology, cardiology and pathology.

Licensed animal health technicians specifically trained in equine internal medicine

and surgery assist our veterinarians and provide patient care during the day and after

hours.

All members of our team utilize state of the art diagnostic and therapeutic modalities

with the common goal of delivering the highest possible standard of compassionate

veterinary care to ill or injured horses, while training the equine practitioners and

veterinary specialists of the future.

Members of our faculty have special interests in

internal medicine

equine surgery

sports medicine

rehabilitation

radiology

neonatology

reproduction

neurology

ophthalmology

cardiology

anesthesiology and pain management

alternative medicine

dentistry

geriatric care

We can perform endoscopy exams on horses at work on the treadmill. We can

perform CT of the head and limbs and nuclear scintigraphy. Our imaging techniques

also include digital fluoroscopy and ultrasound of limbs and chest and abdomen. We

utilize complementary medicine such as acupuncture along with other therapeutic

modalities to manage pain and help athletes perform to their potential.

Veterinarians Committed to Excellence in Horse Health Care – CVHS Equine Specialists Internal Medicine: Lyndi Gilliam, DVM, PhD, DACVIM; Todd Holbrook, DVM, DACVIM, DACVSMR Surgery: Michael Schoonover, DVM, MS, DACVS, DACVSMR; Daniel J. Burba, DVM, DACVS; Megan Williams, DVM, DACVS Reproduction: Reed Holyoak, DVM, PhD, DACT; Candace Lyman, DVM, DACT Anesthesiology: Marjorie Gross, DVM, MS, DACVA; Kip Lemke, DVM, MS, DACVA Ophthalmology: Margi Gilmour, DVM, DACVO; Emily Sharpe, DVM, DACVO Cardiology: Ryan Baumwart, DVM, DACVIM (Cardiology) Radiology: Corey Wall, DVM, DACVR; Mackenzie Hallman, DVM; Carrie Kuzma, DVM

In This ISSUE!

Influence of Diet & Exercise

on Developmental Orthopedic

Disease Prevention

Maintaining Your Horse’s Well

-Being with a Healthy Mouth

AAEP Disaster Relief —

Houston

Equine G-I Discoveries

SFT Castration Clinic

Maintaining Your Horse’s Well-Being with A Healthy Mouth

The old adage "straight from the horse's mouth" may seem more meaningful when you consider that a licensed veterinary practitioner can learn so much about an animal's health by examining its mouth. A Broader Look at Health Equine dentistry is more than just floating teeth. Floating—the term for rasping or filing the horse's teeth—ensures that the horse maintains an even, properly aligned bite plane. While floating is a physical or mechanical process, equine dentistry is much broader and examines the horse's health more systemically. The general goals of equine dentistry include: Improving the chewing of food Relieving pain and treating or curing infection and disease Promoting general health, productivity and longevity Though most people think dentistry is primarily concerned with the teeth and mouth, it also includes the associated structures of the head – for instance the sinuses – and the effect of dental diseases on the health of the rest of the body. Beyond the comfort and good health of your horse, there are other benefits to proper dental care. Your horse will consume feed more efficiently with less spillage or waste and may perform better and live longer. Schedule Exams Regularly Dental disease is a source of pain and infection—it can affect the general health of your horse, especially if undetected or left untreated. Routine examination by an experienced, licensed veterinarian will help detect dental disease and other health problems early—before they threaten the well-being of your horse. These examinations make it much easier to diagnose and treat oral diseases early, preventing more severe and costly problems later. A young horse should have a dental examination when it is foaled, at three months and then every six months until age five. For healthy adult horses, a yearly dental examination is recommended. Horses older than 20 or with a history of dental problems should return to a twice yearly schedule.

Trust Your Veterinarian Certain observations in your horse may be clues to you or your veterinarian that a complete physical examination and a thorough dental exam may be in order. Has your horse’s general attitude changed? Has your horse lost weight? Is the appetite normal? What about the ability to chew? How long does it take to eat? What’s the stool consistency? Is long stem hay present? Are there well-formed fecal balls?

The veterinarian may perform a complete physical examination, and other tests if needed, in order to evaluate the horse for possible risks (i.e., fever, severe anemia, ataxia, etc.) prior to carrying out the dental examination Veterinary practitioners are best qualified to perform dental care on your animal because they are: Trained in equine dentistry, medicine and surgery Licensed to practice dentistry. Equipped with the proper resources to examine, diagnose and treat dental

disease. Prepared to refer particularly severe cases for complicated cases to specialists

with extensive experience. To safely perform a thorough oral examination, sedation and adequate restraint is recommended. Treatment may include antibiotics and anti-inflammatories. All are things that a veterinarian is licensed to provide but an owner or layperson is not. An oral exam should be an essential part of an annual examination by a veterinarian. Every dental exam provides the opportunity to perform routine preventative dental care as well. The end result is a healthier, more comfortable horse. Reprinted courtesy of the American Association of Equine Practitioners.

AAEP Foundation Disaster Relief — HOUSTON

The American Association of Equine Practitioners (AAEP) Foundation’s Equine Disaster Relief Fund is accepting aid to help horses in Texas, Louisiana and other states affected by Hurricane Harvey. Fund donations will be distributed among credible programs and organizations that are helping with recovery and rebuilding efforts in the aftermath and towards preparedness efforts for future disasters. The AAEP Foundation will work with agencies and veterinary members in Texas, Louisiana and other affected states to identify the needs of the equine community. Supplies are not being accepted currently as the catastrophic storm is still occurring. Once the Foundation receives an assessment of need and distribution protocols from the agencies and veterinary members in the afflicted areas, the Foundation will work to support them with supply needs as well. "The AAEP, AAEP Foundation and the equine veterinary community are saddened by the tragic loss of life and incredible destruction and flooding caused by Hurricane Harvey,” said AAEP President R. Reynolds Cowles, Jr., DVM. “We are compelled to reach out, together with our members, horse owners and industry leaders, as part of the effort to support the disaster’s equine victims." To support the impending needs of these equine victims, please donate online at here. Donations by mail can be sent to: Equine Disaster Relief Fund, AAEP Foundation, 4033 Iron Works Parkway, Lexington, KY 40511; (800) 443-0177 (U.S. only) or (859) 233-0147. If you wish to offer assistance with supplies or other resources, please email Keith Kleine at kkleine@aaep.org and you will be contacted with further instructions. About the AAEP Foundation The AAEP Foundation, a 501(c)(3) organization created in 1994, serves as the

charitable arm of the American Association of Equine to improve the welfare of the

horse. Since its inception, the Foundation has disbursed more than $4 million to

support its mission.

Equine G-I Discoveries

Researchers are discovering how the vast and varied microbes in the horse's gastrointestinal tract impact equine health. Much like the intrepid explorers using the Curiosity rover to examine the surface of Mars, searching for evidence of microbes, veterinary researchers are investigating the depths of the equine gastrointestinal tract to learn about microscopic life forms residing there and what they are doing. Scientists are, quite literally, going where no one has gone before. But unlike the surface of Mars, where scientists have only caught glimpses of proof of past microbial life, the horse’s large intestine hosts an extremely diverse range of microorganisms. Identifying all the species and their exact roles, however, has been slow going. Those microorganisms, together with their genomes and their interactions in a particular environment, are referred to as the microbiome. “Studying the equine intestinal microbiome is important because horses are hindgut fermenters,” says Scott Weese, DVM, MSc, Dipl. ACVIM, a professor in the Department of Pathobiology at the University of Guelph’s Ontario Veterinary College. “Changes in the microbiome can result in diseases such as colic, colitis, and laminitis, which are leading causes of morbidity and mortality in horses.” And much like Curiosity and its skilled drivers, Weese is a leader in microbiome exploration, which involves developing new techniques and tools. “Improving our current methods of identifying the trillions of microbes, their genomes, and learning how those microbes interact with their environment will help harness the power of the microbiome to both prevent and treat disease,” Weese says. In this article we will describe scientists’ current knowledge of the equine intestinal microbiome, how it changes during times of stress and disease, and potential ways to maintain or restore a horse’s microbiome after it suffers an insult. The Microbiome in Health “When we originally began studying the microbiome in the early 2000s, we were reliant on standard bacterial culture techniques,” says Weese. “Even though we knew we were going to miss a large number of organisms, it was a place to start assessing specific bacterial populations that we already knew existed. Those included lactobacilli, coliforms, and streptococci.” Researchers developed techniques such as next generation sequencing—one of the most powerful DNA sequencing tools currently available—along the way, which allowed microbiome explorers to identify intestinal microbes based on their genes. For example, Weese and colleagues recently collected fecal samples from six healthy horses and characterized the bacterial composition using next generation sequencing. The most prominent phylum (the major division of living organisms below kingdom and above class) they identified was Firmicutes, followed by Bacteroidetes and Proteobacteria. Within those phyla, bacteria belonging to the genera (further down in the classification) Actinobacter, Lysinibacillus, and Carnobacterium were most common. Interestingly, Weese reports, bacterial populations were different among the six horses. This finding suggests that each horse’s microbiome is unique, adapted to each individual, and that a “standard” intestinal microbiome might not exist. As they uncover the microbes in the intestine—which is as daunting a task as decoding the equine genome—­researchers are simultaneously attempting to determine what functions each serves. Currently, they believe on the whole the equine microbiome is responsible for: Fermenting fiber in the hindgut to produce short-chain fatty acids (SCFAs),

primarily propionate and butyrate, that the horse’s body absorbs into the bloodstream from the GI tract and uses for energy;

Boosting the horse’s immune ­system; Producing antimicrobial products to control populations of pathogenic (disease-

causing) microbes; Physically excluding pathogens; and Inhibiting the production and absorption of bacterial toxins (e.g., those produced

by Clostridium difficile, a common cause of diarrhea in horses).

Newborn foals rapidly develop diverse and rich populations of fecal microbes, leading to a relatively stable microbiome comparable to that of a mature horse by 60 days of age. Photo: iStock

Development of the Microbiome Another interesting aspect of the microbiome is learning where it came from, especially considering that a foal is conceived and develops in a sterile environment (the placenta). In other words, how does a foal’s gastrointestinal tract become colonized with such a rich array of life-saving microbes within hours of birth? To answer this question, Weese and colleagues collected fecal samples from 11 Quarter Horse foals within 24 hours of birth and then routinely until the foals were weaned at about nine months of age. The team extracted and purified DNA from the microbes in those samples and identified the types of microorganisms based on their genome (specifically, the sequence of a region of a certain type of genetic material called 16S rRNA that is like a fingerprint for microorganisms). Microorganisms that have similar DNA are referred to as “operational taxonomic units” (OTUs). They found that: Newborn foals rapidly develop diverse and rich populations of fecal microbes; Those populations change markedly early in life. This is thought to be due to the

acquisition of “transient” microbes that the foal is exposed to by his dam, her colostrum (first milk), and the environment that ultimately do not colonize the intestinal tract;

The numbers of different OTUs decrease early during the foal’s life as the transient “pioneer” microbes clear and the true colonizers become established;

By 60 days of age, foals have a relatively stable microbiome that is comparable to that of a mature horse;

The Firmicutes and Verrucomicrobia phyla, together with other unclassified bacteria, comprise approximately 90% of the bacteria found in the feces of 60-day-old foals. The Firmicutes phylum includes a diverse group of bacteria, including beneficial species involved in fiber fermentation as well as the diarrhea-causing C. difficile and C. perfringens;

The change in the composition of the foal’s microbiome during the first month or so of his life is expected, considering the intestine goes from no microorganism exposure to an abundance following birth, when foals begin to nurse, graze, consume carbohydrates, and practice coprophagy (ingest feces). “A further understanding of the foal's intestinal microbiome will help (owners and veterinarians) manage these animals during a critical part of their lives. ” Dr. Scott Weese “A further understanding of the foal’s intestinal microbiome will help (owners and veterinarians) manage these animals during a critical part of their lives,” says Weese. “For example, we could minimize the impact of foal heat diarrhea (which can occur in the foal during the dam’s first heat post-foaling) and maintain a ‘healthy’ intestinal tract in foals administered systemic antibiotics or subjected to other stresses like ­transportation.” The Microbiome During Disease, Stress The intestinal microbiome is comprised of quadrillions of microbes, and keeping them all happy is imperative to horse health. In adult horses, colic and colitis, laminitis, foal heat diarrhea, and equine grass sickness are the most notable consequences of disrupting the equine intestinal microbiome. To help characterize the exact changes in the equine intestinal microbiome under certain conditions, one research group, including Christopher Proudman, MA, Vet MB, PhD, Cert EO, FRCVS, of the equine division of the University of Liverpool’s Department of Veterinary Clinical Sciences, in the United Kingdom, collected and analyzed samples from the large intestines of horses: 1. Maintained on pasture; 2. Consuming a concentrate diet; or 3. Consuming a concentrate diet and diagnosed with simple colonic ­obstruction and

distension (SCOD), a prevalent form of diet-induced intestinal disease. The researchers extracted and analyzed genetic material to identify the types of microbes present in the microbiomes and further analyzed the intestinal contents to identify the metabolites (e.g., short-chain fatty acids) present. They found: A progressive and significant increase in Lachnospiraceae (in the Bacteroidetes

phylum) and the lactic-acid producing bacteria Bacillus, Lactobacillus, and Streptococcus in response to a dietary switch from pasture to concentrates (Increased lactic acid results in a decreased pH in the large intestine [i.e., more acidic] and a shift in the microbe population in the microbiome.);

A corresponding decrease in bacteria that can break down fiber with that switch; and,

A higher concentration of lactic acid in samples from horses maintained on a concentrate diet and those with SCOD.

In a separate study, a group of researchers from the Faculty of Veterinary Medicine at the University of Liège, in Belgium, analyzed intestinal microbiome samples collected from adult horses with and without diarrhea. They found that the intestinal microbial diversity was significantly less in horses with diarrhea than in horses without diarrhea. They also identified different species of bacteria in horses with diarrhea, including Fusobacteria, than in horses without diarrhea. Finally, they identified C. difficile in 3.7% of tested horses, none of which had diarrhea. Those horses did, however, have decreased “bacterial species richness” compared to horses that did not test positive for C. difficile. Microbiomes Beyond the Gut The microbes that make up the equine microbiome are vast and varied and unique to each compartment of the intestine. For example, the microbiome represented in feces collected from the horse’s rectum is similar to that of the cecum but markedly different from the three regions of the small intestine and the bulk of the large intestine. The colon has the most diverse microbiome of all the compartments studied, says Scott Weese, DVM, MSc, Dipl. ACVIM, a professor in the Department of Pathobiology at the University of Guelph’s Ontario Veterinary College. “Compartments separate from the large intestine are also important and may also impact the overall health of the animal,” says Weese. “For example, one group of researchers from Korea recently began studying the gastric microbiome to determine the role and impact of the gastric microbiome (that of the stomach) on equine gastric ulcer syndrome.” Microbiomes also exist in other body systems besides the intestinal tract. The lung (TheHorse.com/36267) and skin are other examples of organ systems harboring their own microbiomes, yet research regarding these populations remains in its infancy. Stacey Oke, DVM MSc Weese and colleagues also found an alteration in the microbiomes of horses with and without diarrhea. For example, they found predominantly Firmicutes phylum in healthy horses, whereas they most commonly found Bacteroidetes among horses with diarrhea. And they identified Clostridium spp even among healthy horses. “Together these data suggest that diarrhea is not simply caused by the overgrowth of a single pathogen like C. difficile or Salmonella, but colitis may in fact be a disease of ‘gut dysbiosis’ (microbial imbalance) instead,” says Weese. “These results also highlight how important clostridia are. This broad group of often-maligned bacteria plays a critical role in horse health.” Weese and his team have also noted alterations to the intestinal microbiome, resulting in reduced species richness, following systemic antimicrobial therapy. For example, in 2015 they reported that the intestinal microbiome changes following antimicrobial application, resulting in reduced species richness. Tested antimicrobials included intramuscular penicillin and ceftiofur and oral trimethoprim ­sulfadiazine. Finally, the same research team collected fecal samples from 26 mares both pre- and post-foaling, 13 of which developed colic postpartum. They found that the compositions of the mares’ microbiomes before foaling were notably different than they were after; however, foaling itself had a limited impact on the mares’ microbiomes. The team also identified notable differences between mares that did and did not develop colic following parturition. As such, they concluded, “Associations between Firmicutes (particularly Lachnospiraceae and Ruminococcaceae) and Proteobacteria and development of colic could lead to measures to predict and prevent colic.” Keeping the Microbiome Happy One potential way to maintain the equine intestinal microbiome’s health and integrity is through probiotic administration. Probiotics are “direct-fed microbials,” or live yeast and/or bacteria believed to help maintain or restore the health of the intestinal microbiome. Probiotics’ potential mechanisms of action include boosting the horse’s immune system, producing some antimicrobial products, excluding disease-causing microorganisms, and inhibiting bacterial toxins. Examples of probiotics include bacteria and yeast such as Bacillus subtilis, Bacillus licheniformis, Saccharomyces cerevisiae, Lactobacillus acidophilus, Enterococcus faecium, Lactococcus lactis, and Bifidobacterium longum, among others. Weese explains, however, that despite probiotics’ popularity, the clinical evidence supporting their use is lacking. “Whether probiotics are beneficial to horses or not remains debatable and is complicated by the fact that we simply do not know if we are administering the ‘right’ organisms to benefit the intestinal microbiome; if we are offering an adequate dose; if the products are of sufficient quality and actually contain the type and amount of live organisms described on the label; or if it is even possible to orally administer microorganisms to alter the equine intestinal microbiome,” he says. In lieu of a fecal microbiota transplant (yes, this refers to administering “healthy” feces by enema or nasogastric tube), there are ways to help protect a horse’s microbiome, says Kathleen Crandell, PhD, equine nutritionist and consultant to Kentucky Equine Research, in Versailles. “Maintaining horses on forage-based diets with minimal amounts of concentrates and avoiding abrupt changes in diet are key factors involved in gastrointestinal health,” she says. When horses consume high levels of concentrates, some of the starch and sugar therein is fermented in the large intestine rather than digested in the stomach and small intestine. Unlike fiber that is fermented to produce SCFAs that the horse uses for energy, fermented starch and sugar from concentrates produce lactic acid. Remember that abnormal lactic acid production causes a shift in the population of microbes that make up the microbiome. “Hindgut buffers are, therefore, another potential means of maintaining a normal pH in the large intestine, which helps stabilize the microbiome in horses fed high amounts of concentrate feeds to supply adequate energy,” says Crandell. Take-Home Message While Weese and other researchers throughout the world are working to better understand the intestinal microbiome, the number of questions each discovery generates is as vast as the intestinal microbiome itself. “Although we have made a progress in identifying parts of the equine intestinal microbiota, we still only have a superficial understanding of this complex microbial population,” Weese says, adding, “Continued research in this field will revolutionize our understanding of the role of the microbiome in health and disease.” About the Author Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

SFT Castration Clinic

2017 Society for Theriogenology

Equine Castration Clinic

When: Saturday, 11/4/17

Where: CVHS Ranch, Stillwater

To register: CLICK HERE

Only 7 spaces available!!