Riverina Equine Vet



Equine Metabolic Syndrome (EMS) and Laminitis


What is EMS?

Equine metabolic syndrome is a relatively new term used to describe a collection of clinical abnormalities involving altered metabolism in horses. EMS is typically seen in middle-aged horses, however, it can affect a wide range of horses from 5-20 years old. EMS occurs more frequently in pony breeds, Andalusians, Warmbloods, and Quarter Horses.

EMS is characterised by three main defining criteria:

  • Obesity or increased adiposity (excess fat depositions in typical regions of neck crest and fat pads at the base of tail);
  • Insulin resistance (IR), or high blood insulin levels; and,
  • A history of laminitis or current active laminitis.


What is Insulin resistance (IR) and how is it related to laminitis?

After feeding, glucose levels in the blood are high. Normally, insulin is responsible for stimulating the cells of the body to uptake this glucose. In horses with insulin resistance, there is a failure of insulin to stimulate this glucose uptake. Long term obesity is the predisposing factor for the development of insulin resistance. Via a complex process, excess fat cells in the body inhibit the activity of insulin. The body therefore produces more insulin in an attempt to make up for the insulin resistance. The end result is high blood insulin levels, which can have harmful effects on the body, especially the lamellae in the horse’s foot resulting in laminitis.


How is EMS diagnosed?

The goal when diagnosing EMS is to determine if the horse is insulin resistant. The most effective way to assess this is by performing the ‘oral sugar test’. This test involves collecting a blood sample during the morning hours, followed by administering dextrose powder in the feed and collecting another blood sample 60 to 90 minutes later. Blood samples are evaluated for insulin levels.


How can EMS be managed?

Dietary management and exercise (which aid in reducing the risk for developing laminitis) are the two gold standards of managing horses and ponies with EMS.

Dietary adjustments:

  • Restricted diet/reduced caloric intake
  • Feed grass hay or other feed sources that are low in nonstructural carbohydrates (NSC). NSC’s include simple sugars, starch, and fructans. Soaking hay in water for 30 to 60 minutes can help remove these sugars. If only feeding hay, make sure to also offer a balanced hard feed suitable for laminitic horses, such as Speedi-beet.
  • Limit pasture access by using a grazing muzzle or by confining the horse to a drylot, especially during the Spring.


Medical management options for EMS are also available and involve the use of Levothyroxine or Metformin to increase metabolism, which helps horses lose weight and, in turn, reduce circulating insulin levels.