The term 'FIRST STOMACH OF A COW' can be summarized as the RUMEN, which is a five-letter word. The RUMEN is the first of four stomachs in a cow's digestive system and is the largest of the four. It is a fermentation vat that contains bacteria and protozoa which break down cellulose from the plant material that the cow eats. The RUMEN also helps to store food until it is ready to be digested further in the other stomachs.