The Lowdown on EMS
Equine metabolic syndrome (EMS) is a relatively new term to describe a disorder that's not yet well understood. Indeed, EMS is often misdiagnosed as Cushing's syndrome, hypothyroidism or insulin resistance syndrome.
Dr. Rhonda Hoffman, who researches carbohydrate metabolism and insulin sensitivity in horses suspected of having EMS, relates the disorder to Type 2 diabetes in humans.
"Type 2 diabetes is often associated with obesity, and typical warning signs include 'insulin resistance.' In which normal amounts of insulin fail to lower blood glucose levels." She explains. "When this happens, the pancreas must produce more insulin to control blood glucose levels. Insulin stores fat, and thus insulin resistant people (or horses) are extremely efficient at storing fat--and therefore more likely to be obese."
Researchers haven't been able to determine whether a horse can be predisposed to insulin resistance, or why one may be become so--whether it rests on genetics, conditions during gestation, or environmental factors. But they do believe that insulin resistance indicates the onset of EMS. They also know foods high in starch and sugar cause significant spikes in blood glucose, and horses that consume such foods over a long period of time can become insulin resistant.
Another indication of EMS is obesity-associated laminitis. This type of laminitis is mild compared to the painful, disabling kind caused by gastro-intestinal failure. All laminitis stems from changed circulation in the laminae; in obese horses, insulin insensitivity appears to interfere with the endothelial tissue of the laminae, bringing on the disease. Unfortunately, there's currently no medication to treat EMS (those used to manage Cushing's proved ineffective). Experts agree the best way to manage EMS is through diet and exercise. For at-risk obese horses, cutting calories and increasing activity seem to be the best remedies.
This article originally appeared as "Fit (Not Fat) is the Best Color" in the November 2007 issue of Horse & Rider magazine.
