Updated on: 7/31/2019
EMS is most commonly seen in breeds thought of as “easy keepers,” horses and ponies able to put weight on and keep it on even when they don’t seem to eat very much. Breeds that evolved to survive in harsh environments where certain seasons are cold and wet and vegetation is sparse are said to have a “thrifty” gene. While this may have been an advantage to the horse fending for itself, it’s a disadvantage to the modern horse provided with limited turnout, high-calorie grain, and lush pastures. Breeds at a higher risk for EMS due to this particular genetic predisposition include:
EMS is also seen in Arabians, Spanish mustangs, quarter horses, and Tennessee Walking Horses. It is rarely diagnosed in thoroughbreds and standardbreds. Mares and stallions/geldings are equally affected, with most horses between the ages of 5 and 15 when the first signs of EMS, such as laminitis, appear.
History & Exam
Cushing’s Disease, or PPID, is a collection of clinical signs due to the overproduction of certain pituitary hormones. In the early stages of the disease, these clinical signs include:
While certain prescription medications can play a role in the management of Equine Metabolic Syndrome, there is no FDA-approved drug to treat EMS like there is with PPID. Veterinarians recommend a combination of diet, exercise, and medical therapy to achieve a healthy weight, enhance the response of insulin, and reduce the risk of laminitis.
Obese EMS horses may need to be kept off pasture completely -- such as in a dry lot or paddock -- while lean EMS horses may be allowed limited grass access through the use of a grazing muzzle and only when sugars and starches are lowest, from about 3 to 10am. Providing low-NSC hay in either a slow-feeder or small-hole hay net slows the rate of intake, making the hay last longer while prolonging the time spent eating. This is especially helpful for the obese horse who may also have the daily amount of hay restricted to 1.5% of body weight until weight loss occurs.
This disclaimer for workout videos and equipment in people could just as easily be applied to horses:
“To reduce the risk of injury, before beginning this or any exercise program, please consult a healthcare provider for appropriate exercise prescription and safety precautions. “
That is because exercise recommendations for EMS must take into account whether the horse or pony is currently suffering from laminitis or is sound and pain free. Also just like in people, early research in horses suggests that exercise not only helps reduce weight, it also helps improve insulin sensitivity in those affected with metabolic syndrome. While all levels of exercise help burn calories, intense exercise (such as cantering) may be required to affect insulin resistance. Horses should be introduced to exercise gradually at the direction of a veterinarian and the intensity and duration increased slowly over time.
When a horse or pony with EMS does not respond to changes in diet and exercise, the veterinarian may prescribe oral medication to jumpstart weight loss and improve insulin sensitivity. Most commonly used is a high dose of Thyro-L (levothyroxine sodium) for several months while feed is restricted. Once the desired weight loss occurs, the horse can be gradually weaned off the product. The second drug is metformin, used to treat Type II Diabetes in people. Unfortunately, it is poorly absorbed in horses and doesn’t appear as successful in improving insulin sensitivity.
Equine Metabolic Syndrome can lead to serious issues such as laminitis, and, while it cannot be cured, it can be prevented and managed. Veterinarians advise owners of high-risk breeds to observe them closely for signs of EMS (such as fat deposits) and to routinely have dynamic blood tests performed to check for an abnormal response to insulin. Rather than waiting for a bout of laminitis to occur or for blood tests to come back positive, owners of horses at-risk for EMS can already be focusing on maintaining normal weight in their horses through appropriate diet and exercise.
SmartPak strongly encourages you to consult your veterinarian regarding specific questions about your horse's health. This information is not intended to diagnose or treat any disease, and is purely educational.
Article First Published June 2008