Horses are designed to eat a little all the time, Hay/ dry grass should not be rationed. Put hay out in the morning, if it is all gone add more next time. People go out and buy the richest greenest smelling they can find, but then wanna ration it when horse gets fat. Horses are much better off with high volumes of poor grass. Then a commercial feed to adjust weight and minerals up and down. They can eat too much green grass and get to much sugar and cause founder and weight issues, but generally low calorie grass hay or poor pasture grass will keep em healthy.