The Horse

FEB 2018

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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38 TheHorse.com THE HORSE February 2018 C an you name one of the most com- mon causes of lameness in horses? If you said osteoarthritis (OA), you're right. As common as it is, OA remains an incurable disease, and once it presents itself in a joint, there's no going back. Knowing this might cause you to sprint over to the supplement aisle of your local feed or tack store, only to be met with an overabundance of oral joint supplements, each label touting an ability to prevent or slow OA progression. But, believe it or not, most of these supplements' ingredi- ents have no scientific backing in horses, with label claims relying on data extrapo- lated from research performed in humans and other animals. So which oral joint ingredients do have published results specifically in horses? Let's find out. Glucosamine & Chondroitin Sulfate Glucosamine is an amino monosac- charide (sugar attached to the amino acid glutamine). Chondroitin sulfate is a glycosaminoglycan (GAG), an important component of articular (joint) cartilage. Mode of Action Both glucosamine and chondroitin sulfate help protect and pro- vide nutrients to joints. Glucosamine is a precursor to (it transforms, chemically, into) GAGs such as chondroitin sulfate. Chondroitin sulfate gives articular carti- lage resistance to compression. Research Researchers have performed many in vitro (in the laboratory, on tissue samples) studies to better understand glucosamine and chondroitin sulfate's mode of action at the cellular level, either alone or combined. Note that unlike in vivo studies performed on living animals, these experiments do not precisely mir- ror the conditions found in nature. One involved corticosteroid joint injections, which veterinarians commonly admin- ister to promote joint health. However, some corticosteroids can inhibit proteo- glycan (basically a chain of GAGs with a core protein molecule) production, negatively affecting articular cartilage. At the University of Illinois in 2008, Byron et al. found that glucosamine helped protect proteoglycan production when the carti- lage was exposed to a corticosteroid. Using articular cartilage from horse cadaver limbs in 2003, researchers at Michigan State University (MSU) found that glucosamine reduced the expression of genes for matrix metalloproteinases (enzymes responsible for cell degradation) and could help protect joint cartilage. Another team of MSU researchers took articular cartilage from cadaver limbs and exposed it to mechanical impact to simulate a joint injury. By culturing the cartilage with a combination of glucos- amine and chondroitin sulfate (GC), they concluded that GC could help mitigate some of the inflammatory response fol- lowing joint trauma (Harlan et al., 2012). Outside of the lab, Martha Rodg- ers, VMD, of Shephard Hill Equine, in Kentucky, followed 10 hunter/jumper and eventing horses for eight years in a pub- lished field study looking at a glucosamine and chondroitin sulfate supplement's effects on hock injection frequency. Before starting on the supplement, the horses averaged 1.7 joint injections per year at 6.8-month intervals. During the six years they consumed the supplement at the manufacturer's recommended dose, the horses' average number of joint injections dropped to 0.85 every 9.98 months. Rodg- ers did note that six to eight months of consistent GC supplement use is necessary prior to seeing results. It's also important to note that the level of evidence in this small-scale study is not as strong as that of a placebo-controlled and blinded trial. In 2009 at Murray State University, also in Kentucky, researchers evaluated horses' arthritic pain after 150 days of oral GC supplementation and found it did, subjectively, reduce overall pain at a walk and trot and after flexing an arthritic joint. NUTRITION KRISTEN JANICKI, MS TheHorse.com/Nutrition What's in Your Joint Supplement? With myriad equine joint supplement manufacturers claiming their products prevent or slow osteoar- thritis progression, it's important to know which options might be effective. MAMEFRAME PHOTO/MAUREEN BLANEY FLIETNER A look at oral joint supplement ingredients that are backed by science

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