What is rumination?
The act of rumination, or “chewing the cud,” is the regurgitation and remastication of undigested fibrous material before it is swallowed again. As the food reenters the rumen, it undergoes further fermentation. The products of fermentation—in the form of broken-down food particles—then slowly pass to the other parts of the stomach, where the usual digestive juices of the abomasum perform their work. Ruminants secrete copious amounts of saliva that serve to buffer fermentation products in the rumen. It also serves as a fermentation medium for the microorganisms. The total secretion of saliva per day has been estimated at 6–17 qt (6–16l) in sheep and goats, and 105–200 qt (100–190 l) in cattle. Since sheep and goats have an average weight of 88 lb (40 kg) and cattle, 1,100 lb (500 kg), the daily production of saliva may reach about one-third of the body weight. The obligate anaerobic organisms residing in the rumen include ciliates that occur in numbers of several hundred thousand per f
