No Sugarcoating: Diagnosing and Managing the Insulin-Resistant Horse

Insulin resistance can lead to Type II diabetes in people. In horses, it can lead to what is called equine metabolic syndrome (EMS).

"We have diagnosed five or six horses (with EMS) here at Washington State University's Veterinary Teaching Hospital during the past year," said Nicki Wise, DVM, a WSU second-year equine medicine resident. "Most presented with chronic laminitis, which is the one of the biggest problems for horses that have EMS."

Beyond chronic laminitis, a horse's appearance could raise suspicions of EMS.

"Often, horses with EMS have abnormal fat deposits over their neck, rump, tail, and eyes," Wise said. "The disease is closely related to Cushing's disease. Technically it is different, but a lot of the signs are the same. Generally, the disease is not life-threatening, but it will probably shorten their lifespan if these horses are not managed properly."

Ponies, Arabians, and Paso Finos are among the common breeds that the condition is found in, but any horse can suffer from it. EMS also tends to occur in middle-age to older horses, and those that are obese and have a sedentary lifestyle.

"We don't know if obesity leads to insulin resistance or if insulin resistance results in obesity," Wise said. "We don't know which comes first."

To confirm a diagnosis of EMS, veterinarians look at clinical signs, perform a physical exam, and take a blood test to measure serum insulin levels. "The blood test is easy and inexpensive, and can differentiate between insulin resistance and Cushing's disease," Wise said. "If insulin levels are high, the horse probably has EMS."

Read more about diagnosing insulin resistance.

There is no cure for horses with EMS, however, they can benefit from consuming a diet consisting mostly of grass hay that has a low score on the glycemic index, the measure of a food's effect on blood sugar.

"No grain or treats like carrots should be fed," Wise said." Several companies offer commercial pelleted feeds for horses with insulin resistance, which might be an option for picky horses. But always check with a veterinarian before switching feeds.

Regular exercise is also part of a management plan for many horses with EMS, but this requirement can be hard to meet if a horse is suffering from chronic laminitis.

"When switching feed, horses can lose muscle rather than fat, and exercise can help with this considerably," Wise said. "Owners need to understand what condition their horse is in and monitor it so the horse does not waste away.

"If there aren't any lameness issues, exercise is one of the best things that a horse can do. Owners that stick to the changes have horses that feel better, are generally more active and have fewer cases of laminitis," Wise said.

For more information about EMS, or to get help with a diagnosis or treatment plan, contact your local veterinarian. Horse owners in the area can also contact the WSU Veterinary Teaching Hospital at 509/335-0711.

Reprinted from the WSU College of Veterinary Medicine Equine News Fall 2008 issue.

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