Animals which chew the cud are ruminants. Ruminants are mammals that have a four-chambered stomach specialized for digesting tough plant materials such as grass and leaves. They include cattle, sheep, goats, deer, and giraffes. Ruminants are unique in that they digest their food in two stages, first by softening it in a fermentation chamber called the rumen, and then by regurgitating and re-chewing the partially digested food (cud) to break it down further. This process allows ruminants to extract more nutrients from plant material than other herbivores, making them important sources of meat, milk, and other animal products for human consumption.