Insulin is a hormone produced by special cells within the pancreas in order to do many important jobs, one of which is the transportation of glucose from the bloodstream into the insulin-sensitive cells of the liver, adipose (fat), and skeletal muscle.

When foods high in glucose enter the body, more insulin must be released. Insulin resistance (IR) is a condition where the cells of the body do not respond normally to the hormone, causing many serious health problems.

Insulin resistance can be induced by use of corticosteroid drugs or the hormonal abnormalities associated with Cushing’s disease/PPID. IR may also accompany chronic infections such as Lyme disease.

Pregnancy also triggers or worsens IR, preserving precious glucose supplies for the fetus.

However, most cases of IR are associated with equine metabolic syndrome. There is strong evidence that this is genetic. [1][2][3][4]

Equine Insulin Resistance

Insulin resistance is a metabolic type that developed to conserve glucose for key organs such as heart and brain when horses were evolving under conditions of sparse vegetation.

Many modern breeds such as Thoroughbreds, Standardbreds, Quarter horses, full size Drafts and Warmbloods no longer have insulin resistance but those that remain true to their ancestral type still do.

If these horses, ponies, donkeys and mules could live a life similar to their ancestors – working all day or covering 20 miles a day to find sufficient food and water – they wouldn’t have any problems. Few domesticated horses get even close to that level of exercise.

On top of that they are eating diets much higher in hydrolyzable carbohydrates, ESC and starch, which are the components of NSC which cause an insulin response.

Symptoms of Equine Insulin Resistance

Equine insulin Resistance can cause several symptoms such as:

Laminitis is a disease that affects the hooves of the horse, causing elongation and weakening of the laminae and lameness.

Testing for blood insulin and glucose levels is a simple way to diagnose a horse with IR. Once diagnosed, several steps must be taken to manage this condition.

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Treatments for Equine IR

The most obvious change that needs to be implemented is an improvement in diet. Feeding the horse hay that is low in starch and sugar can help prevent laminitis. Hay for horses with IR/EMS should have less than 10% ESC + starch.

One trick to make the hay healthier is to soak it in water which will lower sugar (ESC). Various soaking times have been used but a common guideline is 30 minutes in hot water or an hour in cold water.

Another important change is cutting down the amount of fat the horse consumes; therefore, food rich in fat such as oils and rice bran are not helpful except for amounts needed to provide essential fatty acids and as a carrier for vitamin E. Mad Barn’s w-3 oil provides 900 mg of the anti-inflammatory omega-3 fatty acid DHA and ~890 IU of natural vitamin E in 60 ml (2 oz).