Diseases Caused by Insulin Resistance in Horses

While horses do not become diabetic like humans, many individuals of both species have problems utilizing insulin. As in humans, insulin resistance in horses can lead to many health issues, some of which can be life threatening without proper management.

  1. Definition and Causes

    • According to Balanced Equine Nutrition, insulin resistance can be defined as "a condition in which the cells of the body become less sensitive to the effects of insulin." Because of this lack of sensitivity, the pancreas produces more insulin to keep blood glucose levels controlled. The controlled release of insulin allows glucose to move out of the bloodstream and into cells, where it is used to fuel the cell processes. In insulin-resistant horses, additional insulin is needed for the transfer of glucose into the cells. This improper movement of insulin can lead to a host of health issues. Insulin resistance has been linked to genetics, insufficient exercise, a high sugar diet and mineral imbalance and stress. Many insulin-resistant horses are also victims of Cushing's Disease, which is caused by a benign tumor on the pituary gland; in this case, the insulin resistance is often due to an overproduction of cortisol brought on by Cushing's Disease.

    Health Problems

    • Perhaps the biggest danger for an insulin-resistant horse is laminitis. This extremely painful hoof condition can cause the hoof wall to separate from the laminae of the hoof, allowing the coffin bone to rotate and in some cases drop through the hoof sole. Recovery from laminitis can be a long, expensive process requiring special shoes and a change in management. In some severe cases, the horse will need to be euthanized. In addition, insulin-resistant horses are often obese, which limits their use and predisposes them to laminitis.

    Treatment

    • Insulin-resistant horses will need to have their pasture time limited.

      After blood tests confirm insulin resistance, the best treatments include a change to feeds with a non-structural carbohydrate (NSC) content of less than 10%. Hay should also have an NSC content of 10% or less, which rules out most legume hays. Owners should limit pasture turn-out time for insulin-resistant horses and keep them off pastures altogether during times of high sugar content. There is some evidence that pyrethroid-based fly sprays should be avoided as should supplements with glucosamine. In addition, owners need to keep insulin-resistant horses from becoming overweight.