In the frontier areas of Tibet, yaks are often crossed with Chinese cattle. Such crossbreeds are in great demand as they are especially strong and good natured animals for ploughing and use in caravans. Crosses between yak and cows also give more milk and better meat and are excellent work animals for carrying loads at moderate altitudes. The male offspring of all breeds crossed with yaks are said to be sterile. Of the possible 600 yaks in North America today, about half are females.
Domestic yaks are about the same size as ordinary cattle.
The hair of the wild yak is black and short, except on the flanks and tail where it forms a long, shaggy fringe. Their dense coats and thick hides are necessary to protect them from the bitter cold of the high mountain country. When a yak lies down, it tucks its legs under its shaggy coat to keep them warm. Their horns spread outward and upward, and the head is held low like that of the bison. Wild yaks are usually black.