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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34 February 2019 The Horse | ■ Horses with higher body condition scores had higher ulcer scores; and ■ Risk factors for gastric ulcer develop- ment include feeding unprocessed grains, infrequently feeding a complete and balanced diet, lack of hay or hay- lage, and no grass turnout. Ulcer Treatment and Management As they were learning more about ulcers, researchers were also working to find treatments that would increase gastric pH, buffer stomach contents, and/or allow existing ulcers to heal, Merritt said. In the late 1980s researchers explored the effect of IV and oral ranitidine on gastric pH. In 1992 Merritt and colleagues tested enteric-coated omeprazole granules with good results and, subsequently, helped Merial develop an oral paste. They confirmed its efficacy in 1999, and the product went on to become GastroGard. Another product, UlcerGard, is labeled to prevent ulcers from developing. These are the only U.S. FDA-approved products to treat and prevent gastric ulcers in horses. Merritt said researchers are currently studying a longer-acting intramuscular omeprazole and other oral formulations. Researchers have also recommended strategies to reduce a horse's ulcer risk: ■ Feeding less grain. If horses need extra calories to maintain weight, try adding oil or another fat source to the diet; ■ Providing free-choice forage; ■ Prolonging hay ingestion time by using slow-feeders and/or haynets; ■ Adding alfalfa to the diet, which can aid in gastric buffering; and ■ Looking into nutraceuticals with scien- tific evidence of efficacy. Moving Forward Researchers are still working to better understand ulcers, particularly EGGD, where, Merritt said, other current research directions include: ■ Investigating sucralfate, which might help coat lesions to allow better healing; ■ Finding ways to increase prostaglandin E2 (a chemical the body produces that's involved in inflammation and pain per- ception) production, which decreases acid secretion. Possible methods include sucralfate or corn oil adminis- tration or misoprostol treatment; ■ Taking biopsies from lesions to see if infectious agents are present; ■ IDing causes for different ulcers; and ■ Better characterizing how dietary fac- tors contribute to ulcer development. The Bottom Line "I think it's safe to say that mild ESGD … probably falls within the realm of normality for all equids," Merritt said. "The more severe ESGD lesions, those that extend well up into the squamous region and may bleed, and most likely all EGGD lesions, are more likely due to human-determined condi- tions, such as forced exercise, feeding strategies, housing conditions, increased exposure to infectious agents, and un- doubtedly other factors we have not yet thought of." Understanding Muscle Disorders Stephanie Valberg, DVM, PhD, Dipl. ACVIM, ACVSMR, the Mary Anne McPhail Dressage Chair in Equine Sports Medicine at Michigan State University's College of Veterinary Medicine, in East Lansing, reviewed how five technology advancements have helped her and oth- ers learn more about and discover new equine muscle disorders. 1. Muscle Damage and Blood Samples Researchers knew exertional rhabdomy- olysis (ER, aka tying-up) was a muscle disorder. But they learned significantly more information once they determined they could use a simple blood test to as- sess the amount of muscle damage. The enzymes creatine kinase (CK) and aspartate transaminase (AST) leak out of muscles and into the bloodstream if muscles are damaged. Elevated serum levels of each indicate muscle damage. Valberg said researchers noted a normal marked increase in CK levels after horses with ER worked. Those peaked four to six hours following exercise. 2. Exercise Physiology With the inven- tion of the high-speed treadmill for horses came a new research field: equine exercise physiology. Coupled with the development of a percutaneous muscle biopsy tech- nique, scientists could see what goes on in muscles during exercise and study muscle metabolism as it happened, Valberg said. In the early days of equine exercise physiology, she and colleagues in Sweden studied six Standardbred horses with a history of tying-up and five unaffected control horses. They had horses jog on the high-speed treadmill for 55 minutes at 5 meters per second (roughly 11 miles per hour), collecting samples throughout. They were able to induce ER in three horses, all of which had sudden onset of significantly elevated serum CK levels 15-30 minutes after exercise started com- pared to horses that didn't tie up. In the same study the team tested the theory that increased lactic acid (which muscles produce during intense exercise) buildup in muscle might be involved with ER. However, they found that ER horses did not have much lactate in their muscles following exercise, proving that lactic acidosis isn't behind ER. 3. A Standardized Clinical Approach Valberg said developing this helped vets and researchers discover that not all horses tie up for the same reason or have the same signs of disease. The standard DIETARY DEVELOPMENTS Couple with percutaneous muscle biopsy techniques, high-speed treadmills have allowed scientists to see what goes on in muscles during exercise and study muscle metabolism in real time. COURTESY MARK J. BARRETT/KER

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