Sheep have a natural inclination to assemble in flocks and to follow a leader—characteristics that enable a lone shepherd to handle hundreds of them. Sheep have been domesticated since very early in human history.

Sheep are raised in almost all parts of the world, especially in temperate regions. They provide humans with food, clothing, and many other products. The flesh of young sheep is called lamb; the flesh of older sheep, mutton. Sheep's wool is sheared from their bodies and can be woven into various types of fabrics and carpets. The skins of sheep are used to make numerous leather goods, such as shoes, coats, gloves, and hats. Furs obtained from sheep may be unsheared or sheared.

Mature ewes generally weigh from 120 to 250 pounds (55 to 115 kg). Mature rams range from 175 pounds (80 kg) to 350 pounds (160 kg) or more. Weight depends on the breed and the individual. The fleece is usually white but sometimes gray, tan, or black. Some sheep have fleece covering the head and legs, others do not. In some breeds the hind legs are covered with fleece while the forelegs are bare of wool and covered with hair. In those that have bare faces or legs, or both, legs and faces may be white, black, gray or brown. Some breeds have horns (usually a single pair); others do not. In some breeds only the males are horned; in others, both sexes are.

There are more than 200 breeds of domestic sheep, but only about a dozen are of significant economic importance. The various breeds can be classified in many different ways. A common way of classifying breeds is by the products for which they are primarily raised, as follows:

These breeds are raised primarily for their fine wool. To this category belongs the most famous of all breeds—the Merino, which produces the finest wool. This breed was developed in Spain and has been the basic stock for the development of other types of Merinos, including the American Merino and the Delaine Merino.

The only breed that is raised primarily for its fur is the Karakul.

Most of these breeds are of English origin. They are raised primarily for their meat, although their wool is used also. Included in this group is the Hampshire breed. Hampshires have black or brown faces. The lambs grow exceptionally fast and produce meat of fine quality. Other breeds in this group are the Suffolk, Oxford, Southdown, and Dorset.

These breeds are raised both for their wool, which is of a good quality, and for their meat. The Rambouillet is a dual-purpose breed developed from the Spanish Merino. The Rambouillet has also been extensively used for crossbreeding. The rams usually have large spiral horns; some ewes have stubby horns, but most are hornless. The Corriedale, developed in New Zealand, is considered a good dual-purpose breed. This white-faced breed has fairly long wool covering the body. Horns are lacking in both sexes. Other dual-purpose breeds are the Columbia and Romney.

These breeds are raised primarily in Europe and the Near East. They are raised for their milk as well as for their meat and wool.

Some highly specialized breeds are raised primarily for their milk. Examples are the Awassi and the East Friesian. Some breeds in northern Africa and in Asia produce a coarse wool especially suited to carpet making. Many of these breeds store fat in their tails and are called “fat-tailed” breeds.

In the United States, sheep are raised in practically every state, primarily for meat. Some sheep raisers specialize in purebred stock for breeding purposes.

Sheep are usually bred during the late summer or early fall. Some, however, are bred twice a year. Only one ram is needed for a flock of about 35 to 50 ewes. The lambs are born after a gestation period of about five months. Single births are usual, but twins or triplets are not uncommon. For cleanliness, lambs' tails, which would otherwise grow quite long, are usually docked (cut off) within the first two weeks. For better meat production and easier management, male lambs raised for meat are castrated; they are then called wethers.

Lambs raised for meat are marketed when they are four to seven months old. Those weighing about 100 to 120 pounds (45 to 54 kg) are sold to packinghouses. Smaller ones are sold to “feeders” who take them to feedlots where they are ted grain for rapid weight increase. While meat is the primary product, the wool, skin, bones, intestines, and other parts of the slaughtered lambs are used for various products.

Lambs allowed to reach maturity are raised for breeding and for their wool. Some are also raised for mutton. Sheep are usually shorn of their wool in the spring but sometimes in both spring and fall.

The size of flocks varies greatly. Farm flocks are usually small, ranging from 10 to several hundred animals. Range flocks, consisting of some 2,000 to 10,000 or more sheep, are raised on the open range where they feed on pasture. In these flocks the ewes usually give birth on the open range but in some cases may be provided with sheds. Farm flocks, on the other hand, are allowed to graze on pastures at certain times of the year, but at other times are provided with sheep barns and with feed such as alfalfa, clover, or silage. The ewes generally give birth in the sheep barns.

Although sheep require little care except at lambing time, they are susceptible to various diseases. These include foot rot, foot-and-mouth disease, internal parasites, bloat, and infestation with ticks, lice, mites, grubs, and maggots.

There were domesticated sheep in southwestern Asia about 11,000 years ago. The origin of domestic sheep is not definitely known, but most zoologists believe that they are descendants of relatives of the wild sheep known as urial, argali, and mouflon. Domestic sheep spread from Asia to Europe between 3000 and 1000 B.C.; they were brought to Europe by the ancient Greeks. Sheep were important animals in Biblical times and figure in Jewish and Christian symbolism.

The first sheep were brought to the New World by Columbus on his second voyage in 1493. In what became the United States, the first sheep were introduced, into the Southwest, in the early 16th century by Spanish troops. The American colonies had sheep early in their history.