Largest part of ruminant stomach

Largest part of ruminant stomach Rumen.
The rumen, also known as a paunch, is the largest stomach compartment in ruminants and the larger part of the reticulorumen, which is the first chamber in the alimentary canal of ruminant animals.
The rumen's microbial favouring environment allows it to serve as the primary site for microbial fermentation of ingested feed.