The abomasum is the fourth and final stomach compartment of the stomach in ruminants. It is a secretory stomach similar in anatomy and function as the monogastric stomach. It serves primarily in the acid hydrolysis of microbial and dietary protein, preparing these protein sources for further digestion and absorption in the small intestine.

It secretes rennet, an ingredient used in cheese creation.

The word abomasum is from Modern Latin and it was first used in English in 1706. It comes from Latin ab- + omasum "intestine of an ox," and it is possibly from the Gaulish language.

Even-toed ungulates

Lebmaag