They might be small in size, but weanlings have substantial nutrient requirements to effectively fuel growth and development. Unfortunately, their bodies can make getting these nutrients challenging. They’re unable to fully utilize nutrients in forage until the incomplete microbial colonies in their hindguts develop. In the past, this concern led many to feed weanlings extra concentrates, but recent studies have shown that high-carbohydrate diets can put young horses at risk for developmental orthopedic diseases.

So can weanlings get by on diets high in forage and low in concentrates? Researchers tested three diets to find out.

A team from Michigan State University (MSU), in East Lansing, fed 24 Quarter Horse and Arabian weanlings three diets at 3.5% body weight:

• A high-concentrate diet (High Con), with a 70:30 concentrate-to-roughage ratio;
• An equal diet, with a 50:50 ratio; and
• A low-concentrate diet (Low Con), with a 30:70 concentrate-to-roughage ratio.

“The grain and hay were combined into a pellet so that we were guaranteed horses were consuming the required ratio of hay to concentrate,” said Brian Nielsen, PhD, PAS, Dipl. ACAN, a professor of equine exercise physiology at MSU