Equine Metabolic Syndrome

Equine Metabolic Syndrome (EMS) is a recently recognised condition that describes a collection of clinical signs that increase a horse’s susceptibility to laminitis. The condition is thought to be a similar disease to Type-2 Diabetes found in obese people.

Horses suffering from EMS have excess fat deposits especially in the neck (cresty necks), shoulders and around the tail head. This excess fat produces various hormones including adipokines. These adipokines decrease the body’s sensitivity to insulin leading to insulin resistance. A horse with insulin resistance is unable to regulate their body’s blood sugar (glucose) and this leads to high circulating levels of glucose. It is thought that excess glucose (along with other factors) can predispose a horse to laminitis.

Obesity is becoming a common problem in the general horse population, especially in native breed ponies. These ponies evolved a highly efficient metabolic system to cope with eating poor pasture. Due to the ready access most ponies have to good quality forage all-year-round and the feeding of concentrates their bodies lay down far too much fat leading to clinical obesity. The build-up of intra-abdominal fat by horses is associated with the development of insulin insensitivity, glucose intolerance, and laminitis. Abdominal fat cells (omental adipocytes) are metabolically active, secreting free fatty acids and hormones that might contribute to the persistence and worsening of insulin refractoriness and predispose obesity. EMS is defined as an obese horse with insulin resistance who is suffering (even at a sub-clinical level) from laminitis.

The disease is diagnosed by a physical examination confirming obesity and a blood sample indicating insulin resistance. In most cases a single blood sample can be taken following overnight starvation. It must be noted that not all horses with EMS will have an elevated insulin level in this blood sample. If we are still concerned that EMS is a possible explanation for your horse’s laminitis we can take further tests including monitoring the body’s response to being given glucose orally and by measuring other hormones.

The cornerstones of treating EMS are weight loss and increased exercise. Weight loss can be very difficult to achieve but with a strict diet and patience all horses can lose weight. Obese horses are placed on a hay only diet (with some mineral supplementation) with no access to grass. The hay should be fed at 1.5% of the horses desired body weight (not their actual body weight!). This diet is maintained until the desired body weight is achieved. Exercise helps to reduce weight and increases the body’s sensitivity to insulin. Horses should be exercised for a minimum of 20 minutes moderate exercise 3 times a week. If more exercise can be achieved so much the better.

Metformin is a drug that can also be helpful before significant weight loss is achieved. Metformin increases the body’s sensitivity to insulin helping counteract the negative affects of the adipokines. Thyroid (T4) hormones can also help reduce weight by increasing the horse’s metabolic rate. This can be very helpful in the short term but is not a long-term treatment option.
