Ruminant

A ruminant is a mammal in the suborder Ruminantia within the order Artiodactyla that digests plant material mainly through foregut fermentation. True ruminants are typically hoofed, herbivorous mammals that rely on a specialized stomach and microbial symbionts to break down cellulose before chemical digestion in the lower gut. They are generally characterized by a four-chambered stomach comprising the rumen, reticulum, omasum, and abomasum, and by the habit of chewing cud, or regurgitating partially digested food to chew it again.

In the digestive system, large populations of microbes in the rumen and reticulum ferment fibrous plant material, producing volatile fatty acids that supply most of the animal’s energy. Microbes also synthesize amino acids and vitamins and provide microbial protein when they pass to the abomasum and intestines. After regurgitation and further chewing, ingested material moves to the omasum and then the abomasum, where enzymatic digestion proceeds. This system enables ruminants to extract nutrients efficiently from grasses and other fibrous feeders.

Ruminants include many familiar domestic and wild species, such as cattle, sheep, goats, deer, antelope, and giraffes. They display a range of adaptations in size, habitat, and diet, but share the core foregut fermentation strategy. They are important to human economies for milk, meat, wool, leather, and draft work, and they play significant roles in ecosystems as grazers and browsers.

Not all foregut fermenters are classified as true ruminants. Some related animals, such as certain camelids, have different stomach arrangements or adaptations, and are not always categorized with the classic ruminant group.