The Horse

FEB 2019

The Horse:Your Guide To Equine Health Care provides monthly equine health care information to horse owners, breeders, veterinarians, barn/farm managers, trainer/riding instructors, and others involved in the hands-on care of the horse.

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TheHorse.com | The Horse February 2019 31 The question that followed was: Should we adjust the foal's diet accordingly or the pregnant mare's? (Because of the exponential increase in fetal growth dur- ing the last three months of gestation, supplementing mares in late pregnancy is one way to stock foals with nutrients.) Out of this "research flare" came a New Zealand study showing mare supplemen- tation as most vital to foal bone health. "Since then, the feed industry has universally embraced the importance of trace mineral fortification for broodmare and foal feeds," said Pagan. Over the next decade, however, DOD continued to be an issue, "especially in precocious, fast-growing young horses," he said. Because certain bone lesions appeared to correlate with how fast a foal grows, researchers began looking at the effects of excess dietary energy (e.g., carbohydrates). Theorizing that high-carb diets could lead to osteochondritis dis- secans (OCD, a DOD in which cartilage fails to properly turn into bone), he and his team conducted a study of Central Kentucky farms and found a relationship between glycemic response (carbs' effect on blood glucose) and OCD incidence. "If farms had a high glycemic response, then the farms had a high level of OCD," Pagan said. "Farms with a low glycemic response had a low incidence of OCD." Skeletal Health Bones experience three stages: formation, equilibrium, and de- mineralization. The latter can occur when horses are confined for long periods. When Pagan and his team came across a novel ingredient in the early 2000s purported to suppress bone destruction, called milk basic protein, they conducted a study to determine if it could improve equine bone formation and density. They found that it did, in fact, help prevent bone demineralization in confined horses. They also studied the effect of buff- ered mineral complex (a natural calcium source) on racehorses in training and found it increased bone density fourfold. Digestibility and Nutrient Requirements Different vitamins and minerals have different digestibility and bioavailability (rate of absorption) levels. Whether a vitamin is synthetic or natural can also af- fect its digestibility. Thus, much research over the years has focused on this topic. Scientists have found, for instance, that a natural source of vitamin E is about twice as bioavailable as the chemically different synthetic source, said Pagan. Most recently, he said, researchers have studied the antioxidant nutrient coenzyme Q10 (CoQ10). Pagan explained that in its raw form, CoQ10 is not very digestible, but when it is processed to be water-dispersable it becomes three times as bioavailable. "I think it'll be one of the next big nutrients," he said. Gastrointestinal Health It's well-known that horses are poor starch digesters and don't handle large grain meals well. This can lead to hindgut acidosis—increased large intestine acidity that alters its natu- ral microorganism population, possibly causing colonic ulcers or diarrhea. Over the past few decades, said Pagan, researchers have found that process- ing (e.g., flaking or extruding) grains can make them more digestible in the small intestine and help reduce hindgut acidosis. His team developed a protected sodium bicarbonate (a type of baking soda) to buffer gastric acid. They fed this to horses on high-grain diets, and it reduced the amount of lactic acid hindgut microbes produced. It also reduced lactic acid produced by fructans (nonstructural carbohydrates in grass that can cause hindgut acidosis) in pastured horses. Unintended Consequences Lastly, Pagan described examples of unexpected results from equine research findings. Take furosemide (Salix), for instance, a common diuretic administered to race and performance horses to prevent exercise-induced pulmonary hemorrhage (aka "bleeding"). As it turns out, the drug has a performance-enhancing side effect in that it causes horses to urinate fre- quently and, hence, lose body weight—a desirable reaction in racehorses. Frequent urination also causes horses to lose the electrolytes sodium and chlo- ride and even calcium, upsetting their mineral balance. Pagan said his team found that these mineral levels go into negative balance on Salix administra- tion day. They developed an electrolyte replacement product to encourage horses to drink and correct these imbalances. Another example Pagan used was omeprazole administration to treat gas- tric ulcers. This widely used medication might affect calcium absorption, he said, and scientists have suggested it might result in reduced human bone strength. In one study the KER team found that omeprazole causes a 20% reduction in calcium digestibility in horses. "Owners should recognize that their horses may have higher requirements for calcium when they are administered omeprazole and/or furosemide," he said. The Future Pagan predicted future nu- trition research will focus on nutrigenom- ics (the study of nutrition's effect on gene expression) and nutrigenetics (how genes influence response to nutrition). What we feed our horses might just be affecting our horses' genes and genetic expression. Do We Have an Obesity Problem? "Absolutely," said Pat Harris, MA, Vet- MB, PhD, Dipl. ECVCN, MRCVS, head Kentucky Equine Research staff have been studying the effects of different nutrients, diets, and exercise on horses of various life stages. COURTESY MATT WOOLEY/KER

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