Equine metabolic syndrome (EMS) is an endocrinopathy associated with insulin resistance and the development of laminitis. This disease affects many breeds such as Saddlebreds, Morgans, Tennessee walking horses, and ponies. Unlike Cushing’s disease, this disease can be seen in horses of all ages. The most common clinical signs associated with EMS include: “easy keepers,” fatty deposits such in the neck and tail head, reoccurring laminitis, obesity, and infertility in mares.
In addition to genetic predisposition, common risk factors for the development of EMS include high carbohydrate (grain) diets, low levels of activity, and over use of glucocorticoids or steroids. Horses with insulin resistance have a low sensitivity or few numbers of insulin receptors. This can lead to a state of hyperglycemia due to decreased glucose uptake by tissues from the blood stream. Secondary insulin resistance also leads to decreased blood flow and tissue inflammation. At this time, scientists believe that the lack of blood flow to the laminar tissues of the foot is a leading cause of laminitis in EMS horses. Individuals that undergo massive carbohydrate intake or are left on pasture can undergo a “flare up” of inflammation in their hoof laminar tissues. This leads to the pain associated with laminitis and when left untreated can ultimately lead to laminar separation and coffin bone rotation, otherwise known as founder.
Horses with EMS can be diagnosed based on a combination of history, clinical signs, and blood testing for insulin and glucose levels. Treatment for horses suffering from EMS typically includes lifestyle changes and long-term management changes. These horses should not be given a diet rich in carbohydrates or sugars. They should also be placed on strict feeding with increased exercise in order to lose weight and prevent further fatty deposits from forming. Some medications exist for severely affected horses. However, their efficacy is variable. Overall, horses suffering from EMS that are well managed have a fair prognosis for a long and healthy life. Horses that are more severely affected or are suffering from reoccurring episodes of laminitis have a more guarded long-term prognosis.
Jordan Flewellyn, DVM