Feeding the Endocrine-Challenged Horse

Laminitis risk is the No. 1 reason we worry about equine metabolic conditions such as equine metabolic syndrome (EMS) and pituitary pars intermedia dysfunction (PPID, or equine Cushing’s disease).

Laminitis is the painful inflammation and sometimes separation of the soft laminar tissue on the hoof involved in weight bearing and can be life-threatening. And endocrine disease such as EMS and PPID are behind up to 90% of clinical laminitis cases, says Lisa Tadros, DVM, PhD, Dipl. ACVIM, assistant professor of endocrinology at the Michigan State University College of Veterinary Medicine, in East Lansing.

“Hormonal abnormalities induce abnormal hoof growth and weaken laminar tissues,” said Tadros. She talked about the nutritional management of the endocrine challenged horse at the 2017 Mid-Atlantic Nutrition Conference in Hunt Valley, Maryland, on April 6.

Endocrine Disorders 101

Equine metabolic syndrome can affect horses of any age and is closely linked to obesity. Most horses with EMS are overweight, with abnormal regional fat deposits over areas such as the neck and tail head, but some (particularly those concurrently affected by PPID) can be thin.

Insulin dysregulation (ID) is a hallmark of EMS and causes elevated concentrations of insulin (hyperinsulinemia) that result in abnormal laminar tissue growth, predisposing it to damage and weakening.

“Hyperinsulinemia is the biggest risk factor for laminitis,” said Tadros.

Because EMS is a complex disease that develops as a result of interacting genetic risk factors, physical traits, and environmental influences, proper management (including appropriate nutrition and weight loss) can improve hyperinsulinemia, even in “thrifty” horses that tend to have over-efficient metabolisms.

While it can affect horses of most ages, PPID is most common in older horses—up to 30% of equids in their teens and older develop the condition. This condition causes abnormally high concentrations of several hormones that affect metabolism (including ACTH and cortisol) and induce ID.   Many horses with PPID have hyperinsulinemia, particularly if they’re concurrently affected by PPID; this puts them at risk of developing laminitis. Properly managing PPID can help reduce that risk.

Nutritional Management

Horses with EMS are most often, but not always, overweight. Similarly, PPID horses might be heavy, but some have difficulty maintaining condition because they’re older and have concurrent geriatric health problems, including dental abnormalities.

A horse owner’s perception of weight and body condition is important for initial recognition of metabolic problems. Unfortunately, studies have shown that only 11% of owners can reliably identify obese horses when shown photographs, and up to 40% underestimated their own horses’ weight on a visual scale. Simply put, people tend to underestimate how fat their horses are.

Dietary management is of utmost importance when managing horses with metabolic problems. Overweight horses need to have reduced calorie diets. The Equine Endocrinology Group, a collective of equine clinicians and researchers, have formed a consensus statement on dietary considerations that include:

  • Eliminate all concentrates;
  • Choose grass hay over alfalfa, if possible;
  • Keep horses off pasture during the weight-loss phase and use a grazing muzzle once pasture turnout is re-introduced;
  • Start with feeding at 1.5% current body weight in forage daily and re-evaluate every 30 days. Do not feed less than 1% body weight in forage (this amounts to 10-15 pounds of hay for a 1,100-pound horse);
  • Soak hay in cold water for 60 minutes and discard water before feeding;
  • Limit dietary carbohydrates to less than 10%; and
  • Offer a high-protein ration balancer to provide essential nutrients.

Small- and medium-sized holes in hay nets can help slow down hay consumption and extend consumption time. “The more you can mimic natural environment, the better,” Tadros said.

Some horses lose weight more easily than others (just like people), so patience and careful planning are important.

Metabolically challenged horses that have trouble maintaining weight (such as those with PPID) should get their extra calories from fat, not carbohydrates. Ponies and Miniature Horses are metabolically different from their larger equine counterparts and are especially prone to obesity and EMS. Careful diet planning is essential, and a qualified nutritionist can help guide you. Some horses lose weight more easily than others (just like people), so patience and careful planning are important.

Exercise is essential for burning calories and maintaining muscle tone, assuming the horse is sound enough to handle it. Exercise regimens should be tailored to the individual horse’s ability.

Take-Home Message

Work with your veterinarian to catch signs of metabolic problems as early as possible, and enlist the help of a nutritionist to manage special diets. Weigh all feed and avoid sweet treats. Keep a weekly record of your horse’s weight, and learn about body condition scoring so you can monitor changes in your horse.