Ruminant
A hoofed mammal with a four-chambered stomach that chews the cud, such as cattle, sheep and deer.
Also: Ruminantia, cud-chewer
Ruminants are hoofed mammals that digest plants by fermenting them in a stomach of several chambers and chewing the cud. Cattle, yaks, buffalo, sheep, goats, deer, giraffes and antelopes are ruminants; camels also chew the cud but have a three-chambered stomach and are classed separately. By letting microbes in the rumen break down grass, leaves and straw, ruminants turn plants that people cannot eat into milk, meat, fibre and work. This is why cattle can live on grassland, hill pasture and crop residues unsuited to crops. The methane produced in their fermentation is a significant source of greenhouse gas, and ways of reducing it are being studied.