Holstein bulls and cows are the most popular breed of cattle in the world. They were first bred in The Netherlands and then brought to America in 1857. Holsteins are immediately recognizable by their black and white coloring -- the stereotypical farm bull and cow. Today farmers raise Holsteins for their amazing milk-producing ability: the average cow produces 3,250 gallons of milk a year! They live three to four years, but some have been known to live much longer. Cattle have four stomachs. They graze on a combination of grasses and hay; once the food passes through their first stomach, it's called cud. This cud gets pushed back into their mouth, and the cattle chew on it all day until it is ready to go through the other three stomachs. It almost looks like they're chewing gum!