The biological subfamily Bovinae includes a diverse group of 10 genera of medium- to large-sized ungulates, including domestic cattle, bison, African buffalo, the water buffalo, the yak, and the four-horned and spiral-horned antelopes. The evolutionary relationship between the members of the group is obscure, and their classification into loose tribes rather than formal subgroups reflects this uncertainty. General characteristics include cloven hoofs and usually at least one of the sexes of a species having true horns.
Dairy cattle (also called dairy cows or milk cows) are cattle cows (adult females) bred for the ability to produce large quantities of milk, from which dairy products are made. Dairy cows generally are of the species Bos taurus.
Historically, there was little distinction between dairy cattle and beef cattle, with the same stock often being used for both meat and milk production. Today, the bovine industry is more specialized and most dairy cattle have been bred to produce large volumes of milk. The United States dairy herd produced 83.9 billion kg (185 billion lbs) of milk in 2007, up from 52.6 billion kg (116 billion lbs) in 1950., Yet there are more than 9 million cows on U.S. dairy farms—about 13 million fewer than there were in 1950.