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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36 February 2019 The Horse | TheHorse.com a muscle disorder she and colleagues are currently working to unravel. She said the horses that first showed problems were well-conditioned, very fit 100-mile endurance Arabians that suf- fered intermittent ER, post-race stiffness, increased CK levels, and myoglobinuria (dark brown urine caused by the presence of the protein myoglocin). They'd also develop stiffness about 5 miles into rides that followed about two weeks of rest post-endurance ride. Valberg and team collected muscle bi- opsies from 30 Arabian endurance horses and looked for signs of already-known disorders, to no avail. Eventually, she said, they found breaks and weakness in the affected horses' muscle fiber contractile proteins using an electron microscope. They termed their newly identified condi- tion myofibrillar myopathy (MFM). Because electron microscopy isn't practical for real-world use, Valberg tested whether desmin stain on a biopsy could identify cases. She found that healthy horses' muscle fibers remained aligned, while case horses developed clumps of desmin around their weak myofibrils. They followed their lab work with an exercise test using healthy and affected horses from which they collected muscle biopsies before and after a 45-minute ride. There were no metabolic differences between the groups, but the team found four proteins at rest that differed in case horses compared to controls. They took the same genome mapping approach they used for PSSM but found no genetic markers associated with MFM. They also sequenced genes commonly as- sociated with MFM in humans and found no consistent mutations. Currently, Valberg and colleagues are working to see if they can manage MFM nutritionally and are trialing new supple- ments, developed in conjunction with KER, in affected horses. Managing Joint Disease C. Wayne McIlwraith, BVSc, PhD, DSc, FRCVS, Dipl. ACVS, ACVSMR, is one of the world's leading equine orthopedic researchers and surgeons. He explained how his introduction to synovitis and the addition of arthroscopy to doctors' and veterinarians' toolboxes shaped his career, how joint treatments for horses have changed, and what options might be on the horizon. McIlwraith is a Colorado State University (CSU) distinguished professor in orthopaedics, Barbara Cox Anthony University Chair in Orthopaedic Research, and founding director of CSU's Orthopaedic Research Center. Modern Joint Care Today McIlwraith and other CSU researchers are focusing on how to preserve normal joints and, in the event of injury or wear and tear, reconstitute joint tissue— particularly articular cartilage. They're investigating: ■ Articular cartilage healing; ■ Early disease process detection; ■ Risk factors for musculoskeletal injury; ■ Novel therapies for traumatic arthritis and osteoarthritis (OA); and ■ Rehab protocols, among other topics. There is no cure for OA, but researchers have identified some effective treatment modalities to reduce pain and minimize disease progression, which are broadly classified as symptom- modifying (SM) and disease-modifying (DM) OA drugs. The former can improve signs, but do not slow or halt disease progression. The latter can slow or modify progression, he said. Ideally, vets would like both effects. Disease modification is critical and valuable to managing OA, McIlwraith said. He also noted that removing bone chips and fragments in a timely man- ner, treating severe articular fractures with internal fixation, and treating OCD appropriately are important parts of preventing long-term OA. He touched on several treatment options, including: ■ Intra-articular (IA) corticosteroid injections For some time, "IA cortico- steroids were common, but the dogma was that they were harmful to articular cartilage," McIlwraith said. Eventually, researchers determined that one type of corticosteroid—methylprednisolone acetate—did, indeed, cause articular cartilage degeneration. However, triam- cinolone acetonide, another cortico- steroid, had both SM and DM effects and no negative effects on the articular cartilage. Corticosteroids remain an ef- fective OA treatment for horses; and ■ Physical therapies and rehabilitation This rapidly growing field is an integral part of equine sports medicine, he said. Scientists have studied some of these modalities, including aquatic therapies. "Swimming and underwater treadmills are popular tools after arthroscopic surgery and, increasingly, rehab of non- surgical injuries," he said. In a recent study CSU researchers determined that underwater treadmill work helped decrease OA progression and improved postural stability significantly. Of course, there are also oral joint supplements (OJS), which studies have shown that 49% or more of owners use. "The high prevalence of OA in combi- nation with a lack of a definitive cure has contributed to OJS popularity," he said. Owners typically choose which OJS to use for their horses and generally see them as benign, said McIlwraith. However, because nutraceuticals aren't DIETARY DEVELOPMENTS Dr. Wayne McIlwraith helped pioneer arthroscopy techniques in horses, which has led him on a quest for better equine joint therapies throughout his career. COURTESY COLORADO STATE UNIVERSITY

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