Although a horse is a large animal, its stomach is very small. In fact, Dr. Pratt-Phillips compares the size of a horse's stomach to a football.
Since a horse cannot hold a large amount of food in its stomach at any one time, it must graze throughout the day so it can eat in small intervals. If this is not possible, the horse must be fed several small meals a day. The consequences of large amounts of food left in a horse's stormach could be a ruptured stomach - a serious, life-threatening condition.
The horse's stomach is unique because it has two sections. The top section of the stomach is thin and dry, but the bottom section is thick and mucousy. Since there is quite a bit of hydrochloric acid in a horse's stomach, it is usually best to feed low-carbohydrate diets so ulcers will not form.