Insulin Resistance in Horses

Do you have a horse that you would call an “easy keeper?”  A horse that can seemingly live on air?  If so, there’s a good possiblity he could be suffering from a metabolic condition known as insulin resistance (IR), which is becoming an increasingly recognized problem today.  One of the dangers of insulin resistance in horses is it’s strong association with laminitis, a serious and sometimes deadly condition for horses.  IR is most common in pony breeds, Morgans, Paso Finos, and Norwegian Fjords, but can also occur in Arabians, Quarter Horses, and American Saddlebreds.


Vets describe IR as “the failure of the tissues to respond appropriately to insulin.”  Insulin, a hormone produced in the pancreas, is responsible for the transport of glucose (sugar) out of the bloodstream and into the cells (for energy.)   An IR horse conserves more glucose than other horses and cannot tolerate high carbohydrate consumption.

Most grains, and even many grasses and hays are high in carbohydrates and can be a factor in IR.  Other factors that are linked with the condition include:

  • Obesity
  • Genetic predisposition (especially pony breeds)
  • Lack of exercise
  • Dietary/ mineral imbalances

Symptoms of IR include:

  • Fatty deposits on the crest, rump, or above the eyes
  • Excessive urinating
  • Increased appetite
  • Obesity

While obesity is common among IR horses, not all overweight horses are IR and not all IR horses are overweight.  The only way to know for sure is by having your vet test for blood insulin and glucose levels.

If your horse is diagnosed with IR, special management will be necessary.  If IR is not kept in check, there is a greater likelihood that your horse could develop laminitis.

Management of IR should include:

  • Reducing the sugar/ starch content in your horse’s diet.  This means cutting out all grains, limiting or eliminating pasture grazing, and probably testing your hay to know the NSC (Non-Structural Carbohydrate) level.  Most IR horses need forage with 10% or less NSC.  If your hay has a higher NSC, you can reduce it by soaking it in water (See Katy Watts study on soaking hay.)
  • Use of a grazing muzzle if your horse can handle consuming some grass.
  • Make sure your horse’s diet is balanced in minerals.  Pay special attention to the calcium to magnesium ratio (which should ideally be 2: 1.) You can work with an equine nutritionist on this, if needed.
  • Exercise your horse regularly.  Exercise decreases blood glucose and insulin levels.
  • Maintain your horse’s feet on a regular basis.  A barefoot trim with a short heel and toe is best. (IMHO)

There is a lot of information out there on IR.  Katy Watts website has some invaluable information and I highly recommend it.  If your horse is showing any of the symptoms, please see your vet.  Many IR horses can be managed successfully–I have two of them!


Note: This post is not intended to diagnose or treat any animal.  If you suspect that your horse has insulin resistance, talk to your veterinarian.


Hi! My name is Casie Bazay. I'm a mom, a freelance writer, and a certified equine acupressure practitioner.

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1 Response

  1. April 11, 2013

    […] laminitis something that all horse owners should be concerned about or just owners of Insulin Resistant (IR) or Cushings […]

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