abomasums

The abomasums is the fourth stomach compartment of most ruminant mammals, often referred to as the true stomach because it functions similarly to a monogastric stomach. It follows the omasum and, together with the rumen, reticulum, and omasum, forms the ruminant stomach, but unlike the other chambers, the abomasums is glandular and secretes gastric juice to digest proteins. In young ruminants, the abomasums produces rennin (chymosin) to coagulate milk; in adults, its secretions are primarily hydrochloric acid and pepsinogen.

Anatomically, the abomasums is located in the abdominal cavity, typically on the right side in many species, and it connects to the duodenum via the pyloric canal and sphincter. Its lining contains gastric glands, with distinct regions such as the cardiac, fundic, and pyloric areas that secrete mucus, acid, and digestive enzymes, respectively. The abomasums empties content into the duodenum, where digestion continues.

Functionally, the abomasums provides the glandular, enzymatic digestion stage after the fermented forage is partly processed in the fore-stomach compartments. In pre-ruminants, it is the primary site of digestion from birth; as the rumen and other chambers develop with age, the relative role of the abomasums evolves but it remains essential for protein digestion.

Clinical relevance includes abomasal disorders such as ulcers, abomasitis, and abomasal displacement. Left displacements are particularly common in high-producing dairy cows after calving and may require medical or surgical correction. Proper nutrition and monitoring are important for preventing and managing abomasal disease in ruminants.