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