Ruminants usually eat in a hurry, especially roughage, and most of them are swallowed into the rumen without full chewing. Food is soaked and softened in rumen for a period of time, then retched and returned to mouth, chewed, mixed with saliva again and swallowed into rumen again.
Extended data:
50% of healthy cows are ruminating. When cattle are sick, overtired and subjected to strong external stimuli, ruminant behavior will be weakened or completely stopped. Once rumination stops, food stays in the rumen, which is often expanded due to the gas produced by fermentation.
Cattle ruminate because of the special setting of bovine stomach, which is divided into rumen, reticulum, flap stomach and abomasum, of which only abomasum is the part that secretes gastric juice. The rumen volume of cattle is 100 ~ 300 liters, accounting for about 80% of the four stomachs. There are a lot of microorganisms in rumen, including protozoa (mainly ciliates) and bacteria. Rumen itself does not secrete enzymes, and enzymes in rumen are all produced by microorganisms. Cellulose in feed is fermented and decomposed by enzymes produced by these microorganisms, and most of the formed lower fatty acids are absorbed by rumen wall. The omentum is in front of rumen, close to diaphragm and liver. The inner wall of the omentum is honeycomb, and microbial digestion is also carried out in the omentum.