Farm animals at U.S. zoos

What makes an animal domestic

Domestication is a long, multi-generational relationship in which people take over the care and breeding of another species to get a steady supply of meat, milk, fiber or labor. It changes animals genetically. Domesticated mammals tend to be more docile and tamer than their wild ancestors and often differ in coat color, ear shape and tail form.

Every farm animal traces back to a wild ancestor. The goat comes from the wild goat of Southwest Asia, the donkey from the African wild ass, and the chicken from the red junglefowl of Southeast Asia. In South America, Andean peoples domesticated the llama from the guanaco and the alpaca from the vicuña; neither has wild populations today.

Breeds versus species

Many farm animals are best known by breed. A breed is a group within one domestic species whose offspring reliably share its traits. Highland cattle, the Texas Longhorn and Watusi cattle all look very different, but they are all domestic cattle.

Breeds often carry the history of where they were shaped. Highland cattle were hardened by the wind and rain of the Scottish Highlands and grow the longest outer coat of any cattle breed. Texas Longhorns descend from Spanish cattle brought to the Americas from 1493 that ran semi-feral on Texas rangelands. Watusi horns, which have the largest circumference of any cattle breed, come from the Ankole cattle of east and central Africa.

The cattle family tree also has two main branches. Domestic cattle descend from the extinct aurochs, which split into humpless taurine cattle and the humped zebu. Zebu cattle were domesticated about 2,000 years after taurine cattle, in what is now Pakistan, and are adapted to heat.

Heritage breeds and conservation

Domestic breeds are not assessed on the IUCN Red List, but a breed can still be endangered even when its species is not. A rare breed has a very small breeding population, usually a few hundred to a few thousand animals. Reported causes include the increased use of exotic breeds, neglect of less profitable ones, intensive farming, disease and loss of pasture.

Conservation groups track these breeds in their own categories. The Livestock Conservancy rates a breed "critical" when it has fewer than 200 annual U.S. registrations and an estimated global population under 2,000; it gave that rating to the Texas Longhorn in 2021. The Guinea Hog, a small black pig of the American Southeast, was estimated at no more than 400 animals in 2009. The kunekune pig of New Zealand neared extinction in the 1980s and recovered through dedicated breeding.

Rare breeds are conserved on farms and ranches, and also ex situ at sites such as zoos and conservation farms, or as frozen semen and embryos. Conservation groups value them for their unique traits, which add to biodiversity and cultural heritage and can matter for livestock production in harsh environments.