Grass and hay make up the bulk of a horse’s diet. However, they can also eat things like oats, barley and corn.
Hay and grass are considered structural carbohydrates and are a very important part of horse nutrition due to their fiber content and nutrients. Horses should eat 1.5 to 2 percent of their body weight in foraged grass and hay. They can eat non-structural carbohydrates that are higher in starches and sugars; however, these should not make up a large part of their diet. Some horse feeds contain things like soybean hulls and beet pulp, as these are high in fiber and low in starches.
Horses also need protein. They can get protein from hay and foraged grasses such as timothy or Bermuda grass or from legume plants such as clover and alfalfa. Some horse feeds are also designed to be high in protein.