The stomach of a ruminant has four chambers.

1. The grass enters the rumen and the reticulum, where symbiotic microorganisms digest the cellulose.

2. The cow periodically regurgitates and rechews the cud, to further break down the fibersn.

3. The cow reswallows the cud, which moves to the omasum, where water is removed.

4. The cud finally passes to the abomasum for digestion of the microorganisms by the cow's own enzymes.