Cattle (Bos primigenius) with rumen fistula (an artificial opening that allows scientists to look inside the rumen of an animal) implanted to take digestive samples. The rumen forms the larger part of the reticulorumen, which is the first chamber in the alimentary canal of ruminant animals (cattle, sheep, goats, etc). It serves as the primary site for microbial fermentation of ingested feed. Photographed at the University of Florida.