Because very few bulls are needed to breed with many cows and heifers and to form a complete breeding herd, most male cattle are used for meat. They are "castrated" by removing the testicles to prevent them from being able to breed other cows and heifers, and to take away the male characteristics that are common with bulls. A male that has been castrated before reaching puberty is called a steer. An ox is a male bovine that has been castrated after puberty and is trained and used for draft purposes, such as pulling a plow or a wagon. Cattle can either be horned, which are two bony points coming out on either side of a beast's head, one on each side, or polled, where no horns are grown but a somewhat pointy poll is found at the top of a cow's head.