How many stomach compartments does a cow have?

A cow has four stomach compartments: the rumen, reticulum, omasum, and abomasum. Together, they let cattle digest tough, cellulose-rich plants that humans cannot break down efficiently.

The rumen is the largest chamber and hosts microbes that ferment grass and other fibrous feed. The reticulum helps sort material and forms partly digested food into cud, which the cow regurgitates and chews again. This re-chewing process is called rumination.

The omasum absorbs water, minerals, and some fermentation products while filtering food particles. The abomasum is the “true stomach”: it releases acid and digestive enzymes much like the single stomach of a non-ruminant animal. The digested material then moves into the small intestine for nutrient absorption.

A common mix-up is counting only the rumen, or treating the rumen and reticulum as one chamber because they work closely together as the reticulorumen. Anatomically, however, the standard answer for a cow is four compartments.