Endocrinology

For the Overweight Horse, Every Day is Thanksgiving

By Adam Marcus

Although portly horses need to be put on a diet, it must be done safely, according Megan Shepherd, DVM, PhD, a clinical assistant professor at the Virginia-Maryland College of Veterinary Medicine, in Blacksburg, Va.

The problem is far from purely aesthetic. Overweight horses are prone to a range of potentially serious health problems. The most serious of these is laminitis, but reproductive efficiency and tolerance to heat also can be affected, Dr. Shepherd said at the 2020 virtual meeting of the American Association of Equine Practitioners.

The assessment of body weight in horses generally is done using a 9-point body condition scoring system. “I often see the ribs as a focal point for body condition scoring, but it’s important to consider all 6 sites,” when evaluating an animal, Shepherd said.

Helping an overweight horse lose weight starts with restricting the animal’s intake of dry matter. As a benchmark, owners and caregivers should aim for a target of 2% dry matter per total bodyweight of the horse per day—28 lbs. for a 1,400 lb. animal. However, because dry matter isn’t perfectly dry, that amount likely will require adjustment by a few pounds for water weight.

Another important consideration is nutrient intake, as restricting total calories should not deprive horses of critical vitamins, minerals and protein. Researchers have developed a website (http://nrc88.nash.edu.html) with a calculator that will generate daily requirements for specific nutrients based on the horse’s weight and other factors.

As with people, overweight horses tend to be “motivated by food,” Shepherd said. So physical barriers to overeating might be necessary. These can include hay nets with smaller windows, which will slow down meals, and using grazing muzzles for animals that are at pasture. (Some horses are adept at shedding muzzles, so owners might have to experiment with several kinds before they find one that stays on, Shepherd noted.)

Another critical piece of the dieting process is monitoring. Owners or caregivers should monitor horses on meal plans every 2 to 4 weeks, using weight tape (ideally, the same tape and the same person measuring each time) and the body condition score.

The target weight loss should be roughly 0.5 to 1 point on the body condition score per month, which translates to approximately 25 to 50 lbs per month.

If the animal does not lose much weight, or if the weight loss plateaus, make sure the caregiver is complying with the diet, Shepherd advised. If so, restrict the amount of dry matter further—although don’t drop below 1% of body weight without first consulting with an equine nutritionist.

Shepherd’s talk was sponsored by Cargill.