The feed ingredients used in the ration are much less important than the balance of nutrients in the ration. It is during this phase of their life that most of the developmental orthopedic problems become evident particularly when unbalanced or imbalanced diets are fed. The National Research Council's publication on Nutrient Requirements for Horses gives excellent guidelines on formulating diets for weanlings. The NRC publication particularly stresses the need to formulate diets on a nutrient to calorie ratio basis, matching the energy in the diet to the supply of other nutrients so that those foals grow and not just gain weight. This diet is imbalanced as well.
Similar situations occur with respect the calcium and phosphorus in relationship to dietary energy.
The feed ingredients used to make up a balanced diet are not important. Weanlings as well as other horses can be fed a wide range of feed ingredients. Horses have been successfully raised on corn, oats, nude oats, barley, wheat, milo, rice and byproducts of the milling of each of those grains. Those have been supplemented with soybean meal, cottonseed meal, linseed meal, flax seed meal, fish meal, whey, casein, blood meal, alfalfa meal and urea. The mineral content of the diet has been adjusted with ground limestone, dicalcium phosphate, monosodium phosphate, tripoly phosphate, deflorinated rock phosphate, copper sulfate, zinc oxide, trace mineralized salt and proteinated or chelated forms of several minerals.