A three-year study by nutritionist Sarah Ralston, VMD, PhD, Dipl. ACVN, of Rutgers University in New Jersey, and her collaborators involved feeding draft cross weanlings and yearlings total mixed rations (TMRs) that contained processed forages, a vitamin/mineral suplement, and wheat bran, but little to no grain. This ration was designed to meet or exceed all of the nutrient requirements for growth while avoiding the negative effects of high-starch diets on insulin sensitivity and potential correlation with developmental orthopedic disease.
Insulin resistance has been documented in young horses fed high starch/sugar feeds and has been correlated with an inceased incidence of developmental orthopedic disease, according to Ralston.
Total mixed rations are not new to animal feeds; cattle, dogs, and cats all are commonly maintained on these types of diets. The problem with horses has been to develop a TMR that can be delivered free-choice without causing the animal to become obese or develop behavior problems if fed in restricted amounts.
"I believe TMRs, such as the ones we have been investigating, are the wave of the future," said Ralston. "These are forage-based rations can be formulated to be a consistent and healthy source of nutrition that horses can munch on all day. It avoids the uncertainties of finding good-quality hay and the problems associated with feeding large amounts of grain-based concentrates. We had no wood-chewing or other diet-related issues with horses on the TMRs."
This three-year feeding trial used a cubed TMR that was fed free choice and compared to a traditional ration of long stem