Cattle are herbivorous, meaning that they are plant-eating (primarily grass) animals. Eating grass is called "grazing". They have very strong tongues and strong lower front teeth that help them to graze. Unlike a horse, cattle do not have any upper front teeth. A cow often swallows grass whole. After a cow has eaten its fill and is resting, they return or regurgitate the grass from their stomach to their mouth and rechew it with their very large back teeth to break it down further. This is called "chewing the cud". Other ruminants like deer, sheep and goats also do this. Horses do not. This means that cattle do not need as much food as horses, even though they are about the same size.