The Horse

MAR 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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A22 March 2019 The Horse | AAEP Wrap-Up joints to localize lameness), and imaging. Rather, it's a complementary tool for diag- nosing and monitoring hind PSL injuries. "It provides a quick and objective view of PSL function," he said. "AMG has the potential to provide valuable information from the preventive medicine, diagnostic, and rehab standpoints." Signs of Pain in Ridden Horses If certain under-saddle behaviors become regular occurrences, your horse is likely trying to tell you he's in pain, said Sue Dyson, MA, Vet MB, PhD, DEO, Dipl. ECVSMR, FRCVS, head of Clinical Orthopaedics at the Animal Health Trust Centre for Equine Studies, in Newmarket, U.K. She and colleagues have developed an ethogram (catalog of behaviors and their meaning) for ridden horses to help identify low-grade lameness or pain. Dyson recently compared behavior and pain scores to see if people untrained on the ethogram could reliably use it to recognize pain in ridden horses. "Horses are trying to communicate with us," she said. "We need to learn to listen." Dyson said the original ridden horse ethogram included 117 behaviors. In the current study the team focused on 24 they identified as most closely associated with pain (see She said the presence of eight or more likely reflects musculoskeletal pain. She had 11 assessors—one trained on the ethogram and 10 untrained—watch videos of 21 horses ridden by profession- als, before and after diagnostic analgesia. The horses had various diagnoses of front or hind-limb unilateral or bilateral lameness, kissing spines, or sacroiliac (where the spine meets the pelvis) pain. Before administering diagnostic analgesia, the trained assessor identified three to 12 (an average of 10) behavioral indicators of pain in ridden horses. After analgesia, the trained assessor pinpointed zero to six (an average of three) indicators—a significant decrease in scores, Dyson said. "The untrained assessors also had significant reductions in behavior scores for all the horses after resolution of pain," she said. "The reduction in behavior scores verifies a likely causal relationship between pain and behavior." Dyson also analyzed how often assessors came to the same conclusions and found that both trained and un- trained assessors can use the ethogram to identify likely musculoskeletal pain. But those using it require education on the ethogram for best results, she said. Off-Label Bisphosphonate Use In 2014 the U.S. Food and Drug Ad- ministration approved two bisphospho- nate drugs—clodronate and tiludronate— for controlling clinical signs associated with podotrochlosis (navicular syndrome) in horses 4 and older. Since then, some vets have used these products off-label to treat other equine bone issues, such as bucked shins (microfractures to the front of the cannon bone) or OA in racehorses. But could this be detrimental? Jonathan McLellan, BVMS, Dipl. ACVSMR, of Florida Equine Veterinary Associates, in Ocala, described what the research says. Bisphosphonates and Bone Remodel- ing In healthy horses bone turns over continually—a process called remodel- ing. Cells called osteoclasts break down old bone while osteoblasts create new. This ensures bones remain strong and allows them to adapt to exercise changes or musculoskeletal system stress. It also makes them more resistant to stress- induced injuries. Bisphosphonates inhibit osteoclasts to block excess bone resorption—a hallmark of podotrochlosis. Studies in humans and animals suggest they're anti-inflammatory, chondroprotective (protect joints), and pain-relieving, also. But because curbing osteoclasts interrupts remodeling, the os- teoblasts don't kick into gear to build new bone. Ultimately, this could put racehors- es at risk of more injuries, McLellan said. Questions That Need Answers McLellan said researchers have studied tiludronate for treating lower hock OA, chronic back soreness, and navicular disease. "These studies all yielded favorable results from blinded analysis," he said, but "all horses were older (> 4 years) and none were race- horses, so extrapolation of these results to COURTESY DR. SUE DYSON Researchers determined that both trained and untrained assessors can use the ridden horse etho- gram to identify the likely presence of musculoskeletal pain. Horses are trying to communicate with us. We need to learn to listen." DR. SUE DYSON

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