Cud Cud Cud is a portion of food that returns from a ruminant's stomach to the mouth to be chewed for the second time. More accurately, it is a bolus of semi-degraded food regurgitated from the reticulorumen of a ruminant. Cud is produced during the physical digestive process of rumination. The idiomatic expression "chewing one's cud" means "meditating" or "pondering"; similar expressions such as "he chewed that over for a bit", or "chew on that!" likely have the same derivation. The alimentary canal of ruminants, such as cattle, goats, sheep, alpacas, and antelope, are unable to produce the enzymes required to
Retroperistalsis of humans are weak compared with those of most other mammals. In cud-chewing animals, such as cows, reverse peristalsis can occur so that the food is brought back from the stomach to the mouth for rechewing. When the stomach is filled, peristaltic waves are diminished. The presence of fat in a meal can completely stop these movements for a short period until it is diluted with gastric juices or removed from the stomach. Peristaltic waves start as weak contractions at the beginning of the stomach and progressively become stronger as they near the distal stomach regions. The waves help to