Early EMS Diagnosis and Treatment Minimize Effects

Horses with equine metabolic syndrome (EMS) are at a higher risk for laminitis than the average horse, but veterinarians are learning more about diagnosing EMS early and minimizing its effects, including laminitis. At the Sept. 17-18 Laminitis West Conference in Monterey, Calif., Thomas J. Divers, DVM, Dipl. ACVIM, Dipl. ACVECC, professor and Chief of Large Animal Medicine at Cornell University, spoke about the correlation between EMS and laminitis and discussed the management of these cases.

Genetics, diet, and exercise are the three major factors that can best determine an animal's risk for EMS. Those that develop EMS are usually five to 15 years old, obese, and easy keepers (horses and ponies that maintain or gain weight on a minimum amount of food), often with a cresty neck. Divers said that the fat in the middle of the neck might contain inflammatory mediators, which could lead to insulin resistance (a feature of EMS in which the body doesn't respond properly to the hormone insulin, which is also a feature of diabetes in humans). However, he also said it is not yet known which comes first, the obesity or the insulin resistance.

Divers noted that EMS is more common in breeds that once thrived in harsh conditions. These include ponies, donkeys, domesticated mustangs, Morgans, Norwegian Fjords, Paso Finos, Peruvian Pasos, Arabians, Warmbloods, American Saddlebreds, Andalusians, Tennessee Walking Horses, and Quarter Horses.

While researchers don't yet know why EMS horses develop laminitis, they have several theories.

"One of those is systemic inflammation triggered by episodes of carbohydrate overload in the lower GI tract," said Divers. "Another possibility is insulin toxicity. It's possible that insulin affects the normal mitosis (cell division) of the laminae during hoof growth or has a detrimental effect on blood flow to the laminae."

It's also possible that increased insulin has an adverse effect on glucose (a sugar that provides energy to cells) regulation within the cells."

Divers said that many early changes in the laminae in EMS horses might go undetected clinically. However, endocrine testing of at-risk individuals (those easy keepers mentioned earlier) can allow veterinarians to catch many cases before structural damage to the laminae occurs, get a better prognosis by identifying/treating cases earlier, and monitor responses to treatment.

Obese horses with abnormal fat deposits should be tested for insulin sensitivity early, Divers said, perhaps in March of their 4-year-old year before the warming weather triggers growth of rich grass. For those with borderline results, test again in April after exposure to more rapid growth of grasses.

Restricting diet along with increasing exercise can usually help prevent EMS, even in susceptible horses. Divers said that levothyroxine (a thyroid hormone) is currently the best medical treatment for EMS if diet and exercise alone don't work. Metformin has been shown to work, but he noted that its effects can be erratic.

A recent study on the prognoses of horses and ponies with EMS and laminitis showed that an animal with previous laminitis episodes might not develop as severe clinical signs in a subsequent episode. Divers noted, however, that their long-term prognoses after repeated bouts of laminitis was worse than that those with only a single episode, confirming the importance of early detection and treatment of EMS and associated laminitis.

About the Author

Tracy Gantz

Tracy Gantz is a freelance writer based in Southern California. She is the Southern California correspondent for The Blood-Horse and a regular contributor to Paint Horse Journal, Paint Racing News, and Appaloosa Journal.

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