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Feeding Horses with Endocrine DisordersBy Kentucky Equine Research Staff · August 22, 2014

Despite a willingness to manage aging horses, advanced nutrition for such horses, and improved knowledge about the health needs of this horse population, there remain two health issues that plague older horses: equine Cushing’s disease (also called pituitary pars intermedia dysfunction, PPID) and equine metabolic syndrome (EMS). These endocrine (hormone-related) disorders are important because horses with PPIDor EMS are at risk for laminitis, which is a life-threatening condition. In fact, an estimated 50-80% of horses with PPID/EMS suffer from laminitis.

Dr. Ray Geor from Michigan State University suggests* that weight management and control of insulin levels are two important ways to help maximize quality of life and longevity in horses with laminitis associated with PPID and EMS.

First, it is important to ensure that all horses, particularly older horses with endocrine disorders, maintain an appropriate body condition. Being thin isn’t a good thing, but being overweight can contribute to insulin resistance and other metabolic derangements and can promote laminitis. “Eat less, exercise more” should be your mantra if your horse has a tendency to be on the heavy side.

Assess exactly what your horse is eating, including supplementary hay, pasture quality, grazing time, supplements, and treats. In most older horses with PPID/EMS, forage or forage substitutes should be the basis of their diets. Excessive feeding of treats should be avoided. If offering hay, use late-maturity hay instead of early maturity because the later-cut hay has a lower energy content. Feed approximately 1.25% body weight in dry matter intake to achieve a safe level of weight loss. Finally, rather than feeding your horse only once or twice daily, consider offering more frequent meals or try using a nibble bag or grazing muzzle to slow intake.

Second, because insulin levels are frequently higher in horses with PPID/EMS, affected horses can have exaggerated insulin responses following a meal (particularly meals high in nonstructural carbohydrates, such as oats, barley, and corn). Recall that insulin is secreted after meals to help tissues such as muscle absorb glucose (sugar). Horses with PPID/EMS fail to respond to insulin and continue to produce insulin to deal with the high glucose levels. To help control those high insulin levels, avoid feeds and grains high in nonstructural carbohydrates, and restrict or eliminate grazing on pasture.

As mentioned above, the diet should be hay-based and contain grass hay with lower energy and limited nonstructural carbohydrates. If a horse does require additional energy, ration balancers, feeds low in nonstructural carbohydrates, molasses-free sugar beet pulp or fat (oil) may be offered.

Together, these dietary modifications can help older horses with endocrine disturbances maintain longer, happier, and healthier lives.

*Geor, R.A. 2013. Dietary management of endocrine disorders in the older horse. Proceedings of the American Association of Equine Practitioners Annual Convention, Nashville, Tennessee.