Rumen

The rumen, also known as a paunch, forms the larger part of the reticulorumen, which is the first chamber in the alimentary canal of ruminant animals. It serves as the primary site for microbial fermentation of ingested feed. The smaller part of the reticulorumen is the reticulum, which is fully continuous with the rumen, but differs from it with regard to the texture of its lining.

Read more about Rumen:  Brief Anatomy, Stratification and Mixing of Digesta, Digestion, Microbes in The Reticulorumen

Other articles related to "rumen":

Rumen - Microbes in The Reticulorumen
... for 40-60% of total microbial matter in the rumen ... Although protozoa are not essential for rumen functioning, their presence has pronounced effects ... numbers, the fungi still occupy an important niche in the rumen because they hydrolyse some ester linkages between lignin and hemicellulose or cellulose, and help break down digesta particles ...