Sheep are ruminant members of the Bovidae family. They belong to the genus Ovis, which contains three species, Ovis musimon, Ovis orientalis, and Ovis aries.
Sheep evolved about 2,500,000 years ago. They were the first animals to become domesticated, approximately 9,000 to 10,000 B.C. Ovis musimon, the European moufflon, is still found wild in Sardinia and Corsica and 0. orientalis , the Asiatic moufflon, also roams freely in Asia Minor and the Caucasus. There are specimens of these wild species in many zoos. The European moufflon is horned, with a massive circular rack and its wool coat hidden under the long guard hairs. The rams will weigh up to 600 lb (270 kg), as heavy as some of the smaller cattle breeds. The Asiatic moufflon is similar in appearance to the European moufflon, but weighs one-third less. Over the years, the domesticated sheep has undergone so many changes through controlled breeding that it is now its own species, Ovis aries.
Sheep domestication and the harvesting of wool is an ancient practice. Wool fabrics have been found in prehistoric ruins 10,000 years old. The beginnings of sheep domestication seem to center in Iran, Iraq, and Turkey around 6,000 B.C.; then the practice was spread by the Phoenicians to Africa and Spain. By 4,000 B.C. domesticated sheep had appeared in China and the British Isles. On an uninhabited isle near St. Kilda in the Scottish Hebrides is a flock of primitive sheep called Soay sheep, which are survivors of the Bronze age. They exhibit the characteristics halfway between the moufflon and modern breeds, including brown coloring, massive curved horns and kempy wool. The neighboring sheep farmers pay an annual visit to this isle, where they round up the sheep, shear and cull the flock, then depart for another year, leaving the flock to fend for themselves.
Spanish farmers developed the Merino breed of sheep in the sixteenth and seventeenth centuries, and the fineness of its wool is unsurpassed even today. In the seventeenth century Robert Bakewell, in England, using his newly discovered breeding methods developed the Southdown and the Leicester, led the way to improvements in other breeds. Because most sheep breeders in England were small farmers, they created several distinctive breeds to meet requirements of the their locals and to satisfy the local wool markets. So some of the breeds were developed for the quality of their meat, some for their fine wool, some for their coarse wool (for carpets, etc.), some for their ability to produce milk, and others for their hardiness.
The Merino was so outstanding that Spain refused to export the breed in an attempt to keep its monopoly. Louis XVI of France asked for and received a flock of 366 and used them to build his own breed of fine wools, the Rambouillet. Both the Merino and Rambouillet have since been the basis for upgrading the qualities of wool for other breeds.
The Finnish Landrace breed is noted for its tendency to have a litter of young rather than a single lamb. The Russian Romanov also has multiple births, and breeders are now importing these into the United States, hoping to incorporate this trait into the established types. The Merino, prized for its wool, does not reproduce as successfully as other breeds, so a program to interbreed the Merino with the Landrace or Romanov would benefit both breeds.
In the United States, sheep are not commonly thought of as milk producers, but there are many cultures that commonly use the milk for drinking, cheese making, and butter. Worldwide, sheep milk production was estimated at 9.04 million tons in 1988. Sheep milk is much richer than cow's milk, though; cow's milk contains 3-6% butterfat, and ewe's milk contains 6-9%. A single ewe produces an average of one pint of milk per day.
French Roquefort cheese is made from ewe's milk. In the United States, a similar cheese is made from cow's milk and is called blue cheese. The blue streaks are caused by bacterium Penicillium roqueforti. Feta, originally from Greece, is also made from sheep's milk and is produced in several countries around the Mediterranean. The very popular Akawi comes from the area of Acre in Israel. Numerous local brands of white cheese are also found in the Balkans.
Sheep skins were the source of parchment from around 600 B.C. through the Middle Ages. The invention of printing, though, spurred the need for and manufacture of paper substitutes. Sheep parchment was one of the materials onto which the Dead Sea Scrolls were lettered, as well as most of the illuminated manuscripts of the monasteries. It is still used on occasions for degrees or meritorious citations, though true parchment is most often replaced by a paper product that resembles it.
Next to meat and wool, probably the most noted of sheep products is the Scottish haggis, the main course for festive times. It is a mixture of diced heart, liver, and lungs with turnips and oatmeal, all stuffed into a sheep's stomach and baked. When ready to serve a bagpiper precedes it into the dining hall. The sheep's blood, gathered during the slaughter, is the main ingredient in black pudding or a beverage. Soap and tallow come from the hard white fat, and some bones became shuttle bobbins in the weaving process. The intestines are the source of catgut.
Christopher Columbus brought over sheep, horses, and cattle on his second, third, and fourth voyages to the New World, as did many explorers who followed him. These animals served as the basic breeding stock for the missions that Spain was setting up in the New World. A century after, sheep numbered in the hundreds of thousands in Mexico and the Southwest, and their numbers continued to increase in spite of predators, Indians and other setbacks.
The Bighorn sheep is native to North America, but had no part in the development of the domesticated sheep business. In fact, the sheep which were imported from Europe carried and spread diseases that decimated their wild cousins. Predators such as the coyote, the eagle, and mountain lion also that take their toll on wild sheep populations. Recently, it was discovered that the presence of llamas, donkeys, and cattle in the flock will help prevent predation. Certain breeds of dogs that are raised with the flock also protect the sheep by attacking predators.
Most of the sheep flocks on the western United States ranges carry Rambouillet and Merino blood, as they are often bred for their wool. It is the custom to castrate the ram lambs in these flocks and to use purebred rams from outside the flock to upgrade the wool. These males are retained for three to five years for shearing, and when the quality or quantity of their coat begins to decrease, they are sent to market and sold for meat.
Ewes are kept longer than the rams, up to seven or eight years, as they also produce a lamb every year in addition to their wool. A single lamb is the norm, but through selective breeding the farmer can sometimes achieve a larger lamb crop. Lambs bred for meat come from smaller farm flocks in the eastern and midwestern areas of the country.
Wool production in the United States has steadily declined since World War II, in spite of government subsidies, and now about 75% of the country's wool is imported. Australia produces about 25% of the world's wool. The development of cheaply-made synthetic fibers has greatly reduced the demand of the natural fibers such as wool.
The Merino and the improved British breeds constitute the majority of the modern breeds. Nearly all have a white fleece, as brown or black wool will not dye as readily. Wool is graded depending on the quality and length of the fibers. The blood system, most commonly used, grades the fleece as Fine, 1/2, 3/8 1/4, Low, and Braid.
See also Livestock.
J. Gordon Miller
Science EncyclopediaScience & Philosophy: Semiotics to Smelting