The term oxen, broadly used, refers also to closely related animals, such as the buffalo and the bison . Narrowly used, ox refers to a mature castrated male used for draft purposes. In referring to domestic cattle a grown male is a bull, a grown female a cow, an infant a calf, and an animal between one and two years old a yearling.
Some cattle are naturally hornless.
A smaller species, the Celtic shorthorn, was the most important domestic ox of the Stone Age and may also be involved in the ancestry of B. taurus. The zebu , or Indian ox, B. indica, is the humped domestic species of Asia and Africa. Several B. indica breeds have been developed in the United States into the Brahman breed. The yak , B. grunniens, and other cattle species, wild and domestic, exist in Asia. Domestic cattle were first brought to the Western Hemisphere by Columbus on his second voyage.