Diet Restriction for Equine Weight Loss

Equine obesity is an increasingly common problem, leading many owners to seek safe weight loss solutions for their horse. In most cases veterinarians and nutritionists advise restricting diet and increasing exercise, but with some horses--those suffering from laminitis, for instance--exercise might be contraindicated. This leaves dietary restriction as the only means for weight loss, making it that much more difficult.

To that end, a recent study carried out at the University of Liverpool, in the U.K., partly funded by WALTHAM and led by Caroline McGregor-Argo, BVSc, BSc, PhD, Dipl. ECAR, MRCVS, focused on diet restriction (DR) as the sole means of achieving weight loss in the obese equid.

Employing 12 overweight horses and ponies divided into two feeding groups, the researchers reduced animals' dry matter (DM) intake to 1.25% of each horse's body mass (BM) and studied weight loss rates over a 16-week period. They estimated the two diets to be nearly equal in calories: Group 1 received 0.8% BM chaff-based complete feedstuff and 0.45% BM grass hay, while Group 2 received 1.15% grass hay and 0.1% nutrient balancer. McGregor-Argo explained that the purpose for having two feeding groups was "to test the hypothesis that we could substitute some of the hay diet for the proprietary feed (to have greater nutrient control) without compromising weight loss."

Researchers found that the horses' weight loss response to DR varied greatly. While some animals lost weight, others were resistant to weight loss, either maintaining or gaining weight at the current level of DR. In an extension study lasting four more weeks, researchers retained four of the more weight loss-resistant animals and reduced this subgroup's diet to 1% BM to see if weight loss could be achieved.

Key findings included:

  • Most animals lost the greatest amount of weight during the first week, with weight loss rates gradually slowing or halting by Week 16;
  • Most horses' baseline plasma insulin levels decreased during DR; and
  • The four extension study horses lost weight at more than three times their earlier rates when restricted to a 1% BM diet.

"Horses have a different metabolism than people and cannot tolerate extreme dietary restriction in the same way," McGregor-Argo cautioned. "We would recommend that restriction below 1.25% should be used only when absolutely needed, and that this should be conducted under veterinary supervision."

The study, "Weight loss resistance: A further consideration for the nutritional management of obese Equidae," appeared in The Veterinary Journal in October 2012. The abstract can viewed online.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.