Cows do not have top teeth in the front of their mouths. They do have molars in the top-back portion of their mouths. Because cows are herbivores, they use their bottom teeth, top dental pads and their tongues to pull grass into their mouths for feeding.
Once a wad of grass is partially chewed, the cow swallows it. The cow then regurgitates it and chews it again using the top and bottom molars in the back of its mouth before swallowing it again. Cows spend 7 to 10 hours chewing cud, or regurgitated food, each day. Because cows have no top teeth, they are unable to bite others.