Rumination and Eructation.

 Rumination is what is commonly called chewing the cud. When a ruminant animal grazes, it doesn't do much initial chewing. Later when the animal is at rest, boluses of coarse roughage are regurgitated up into the mouth, mixed with saliva, chewed thoroughly and reswallowed. The finely ground material sinks into the depths of the rumen.

Eructation is the periodic belching of rumen gas. This is necessary to eliminate the gas that is produced as a byproduct of microbial fermentation.