Both the forage and concentrate portions of the horse's diet supply protein. The quality of hay or forage fed will greatly influence how much protein is required in the concentrate. Cereal grains will also supply protein in the diet. But depending on the class of horses being fed, the forage component of the diet may not be able to meet their protein requirement. To meet the protein requirement of the young, growing horses you will need to use a protein supplement.
Soybean meal is the most common protein supplement used in horse rations.
Other protein supplement sources are available such as linseed meal, cottonseed meal, dried skim milk or commercially prepared protein supplements which may contain a combination of the above ingredients. Minerals Minerals are needed by the horse's body for various purposes, ranging from serving as components of the horses skeletal system to maintaining nerve conductivity, muscle contraction and electrolyte balance. Therefore these minerals need to be supplied to the horse in the greatest amount and are of most concern in formulating horse rations. Horses are more likely to suffer from a lack of calcium and phosphorus than from lack of any other mineral. Always provide salt to the horse free-choice.