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).

w-3 Oil

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  • Promotes joint comfort
  • Helps to fight inflammation
  • Skin & coat condition
  • Palatable source of Omega-3's

Specific vitamins and minerals, such as magnesium, can benefit a horse with insulin resistance.

Horses with EMS/IR are also prone to iron overload which is known to worsen IR in other species. [5] Higher intakes of copper and zinc are helpful in counteracting iron’s competition for absorption.

Mad Barn’s AminoTrace+ mineral and vitamin supplement has been specifically formulated to meet the needs of insulin-resistant horses.


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  • Complete mineral balance
  • Supports metabolic health
  • Formulated for IR/Cushing's
  • Hoof growth

Equine Management

Although not all horses with IR are obese, most usually gain weight, so an increase in exercise is very important for the affected horse, as long as it is not laminitic. Exercise is actually an excellent way to increase sensitivity to insulin, better than diet alone. [6][7]

Physical activity cannot be ignored when dealing with insulin resistance; it must be combined with a diet change to help improve the horse’s condition.

Lastly, because laminitis is a serious threat linked to equine insulin resistance, the horse’s hooves must be given proper attention in order to minimize the effects of high insulin.

It has been known since the early days of studying this condition that the laminae are weakened and lengthened even in horses not showing any pain. [8]

Maintaining a trim with a short rounded toe and palmar angle no higher than 5 degrees helps to avoid undue traction and pressure on the laminae.

Equine insulin resistance is a serious condition that is connected with Cushing’s disease and laminitis that must be managed thoroughly and carefully.

Nevertheless, with a balanced diet, good hoof care, and a healthy amount of exercise, horses with insulin resistance can live a normal life.

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