In Ruminantia, a complex digestion characterized by a stomach having three or four parts. In the rumen millions of symbiotic bacteria and other cellulase-producing micro-organisms partially digest the cellulose-rich food. The enzyme cellulase cannot be made by mammals themselves. After some time the partially digested food (cud) is assembled into pellets in the reticulum ready for regurgitation. The regurgitated cud is chewed thoroughly before passing to the omasum and abomasum where normal digestion occurs. In some ruminants the rumen and reticulum form a single large chamber.
Subjects: Zoology and Animal Sciences.