Grass is a lot tougher than it looks. It contains cellulose, a strong fiber and silica, the same material that's in glass. It would wear out human teeth quickly! The wildebeest, however, is built for eating grass. But digesting this tough material can take a long time. The wildebeest's teeth keep growing as they are worn down by its tough diet. Its stomach has four chambers. (Yours only has one) The grass starts out in the first chamber. But look what happens next! The wildebeest regurgitates the grass - now called cud - and chews it to break it down. As the grass moves through the stomarch chambers, bacteria break down the tough cellulose. The wildebeest's long digestive tract absorbs the nutrients. Nearly three days later the rest becomes poop!