For horse owners and barn managers, Equine Metabolic Syndrome (EMS) is a challenging condition to manage. How do you know which hays and feeds are safe and how should pasture turnout be regulated?

Horses and ponies diagnosed with EMS cannot effectively metabolize dietary sugars due to a reduced insulin sensitivity. These horses are often overweight or obese and have an increased risk of laminitis.

Metabolic horses need to be fed a diet with reduced sugars and starches. It’s also important to manage their weight and regulate caloric intake while balancing vitamins and minerals.

Proper dietary management is key to helping horses with EMS live long and happy lives and reducing the risk of laminitis or other complications.

If your horse has been diagnosed with EMS, work with the equine nutritionists at Mad Barn to create a personalized feeding plan that supports metabolic health.

What is Equine Metabolic Syndrome

Equine Metabolic Syndrome is a common condition affecting horses of many breeds. The American College of Veterinary Internal Medicine describes the EMS horse as having: [1]

  • Increased fat deposition throughout (obesity) or in specific locations (e.g. cresty neck)
  • Abnormal insulinemic or glycemic responses to a glucose test (oral or IV)
  • Laminitis (clinical or subclinical) that has developed without a recognized cause

Equine Metabolic Syndrome is not considered a disease, but rather a metabolic type associated with an increased risk for the development of laminitis.


EMS is a complex syndrome that involves insulin resistance and oxidative stress. [2][3]

Horses diagnosed with EMS may also have elevated triglycerides or leptin in the blood. [1]

The overt systemic inflammation observed in human metabolic syndrome is not consistently found in equine studies. [29][30]

Insulin Resistance

Insulin resistance describes an impaired cellular response to the hormone insulin. This hormone is secreted by the pancreas when blood sugar (glucose) is high. Blood sugar levels rise after a meal, particularly when there is high sugar and starch content in the diet.

Insulin helps lower blood glucose by stimulating cells of the liver, muscle, and adipose (fat tissue) to take in glucose from the blood. In a normal horse, blood glucose levels will return to normal by two hours after a meal.

In horses with insulin resistance, the cells of the liver, muscle, and adipose don’t respond well to insulin. Glucose may rise higher and stay elevated in the blood for longer which triggers further insulin secretion.

Horses with EMS have high levels of circulating insulin (hyperinsulinemia) and rarely have elevated sugars (hyperglycemia).


Although not the cause for the development of EMS, obesity is common in horses diagnosed with EMS and contributes to reduced insulin sensitivity.

However, some horses with EMS might appear normal without general or regional fat deposition. [1]


EMS is most commonly observed in obese and senior horses. However, signs of metabolic syndrome such as easy weight gain can begin to appear once the animal has stopped growing.

An estimated 18 – 27% of horses and ponies have insulin resistance, and up to 51% of horses in the United States are considered obese. [4]

Your horse’s risk of equine metabolic syndrome is affected by genetics (breed), diet and exercise level. Careful attention to diet and exercise can help reduce their risk even if they are genetically predisposed to developing EMS.

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