Cows have a complex digestive system that consists of four stomachs, which together have a capacity of 115-200 litres, through which the food passes during digestion. The ingested grass first goes into the first stomach, which is very large and is called the rumen (or belly), where the first phase of digestion takes place. The fermented grass then passes into the reticulum (or cap), which acts as a funnel and selects the fragments of food that are still too large, which are regurgitated and returned to the cow's mouth, which chews them again (rumination). The cow spends 5 to 8 hours a day ruminating. The mush created as a result of rumination then goes into the omasum (or centopelli or book), which has the function of absorbing liquids, and finally into the abomasum (or quaglio), which is the actual stomach, as we are used to understanding it, where the food is finally digested before passing into the intestine.