ruminant, any of a group of hooved mammals that chew their cud, i.e., that regurgitate and chew again food that has already been swallowed. Ruminants have an even number of toes on each foot and a stomach with either three or four chambers. In the first chamber, called the rumen, the food is mixed with fluid to form a soft mass, the cud, or bolus. The regurgitated cud, after having been slowly chewed, is swallowed again, and passes through the rumen into the other stomach chambers for further digestion. The group, a suborder of the mammalian order Artiodactyla, includes goats, sheep, cows, camels, and antelope.

Any cud-chewing ungulate, including antelope, camels, cattle, deer, giraffes, goats, okapis, pronghorn, and sheep. Most ruminants have a four-chambered stomach, two-toed feet, and small or absent upper incisors. Camels and chevrotains have three-chambered stomachs. Ruminants eat quickly, storing masses of grass (grazers) or foliage (browsers) in the first stomach chamber, the rumen, where it softens. They later regurgitate the material, called cud, and chew it again to break down the undigestible cellulose. The chewed cud goes directly to the other chambers, where various microorganisms help in its digestion.

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