Domestic sheep
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[Photo] A flock of sheep. These particular sheep belong to a research flock at the US Sheep Experiment Station near Dubois, Idaho, USA Image taken from http://www.ars.usda.gov/is/graphics/photos/ (Image Number K4166-5).

The domestic sheep (Ovis aries), the most common species of the sheep genus (Ovis), is a woolly ruminant quadruped. It is probably descended from the wild mouflon of South Asia and Southwest Asia. Female sheep are referred to as ewes, intact males as rams, castrated males as wethers, yearlings as hoggets, and younger sheep as lambs. In sheep husbandry, a group of sheep is called a herd, flock or mob. Sheep husbandry has a vast lexicon of terms, which varies frequently with region.

The sheep is related to the goat, both belonging to the goat antelope subfamily Caprinae, itself part of the family Bovidae. However, the genes of sheep and goats differ so greatly that cross-species hybrids rarely occur, and are always infertile. A hybrid of a ewe and a buck is called a sheep-goat hybrid, not to be confused with a geep, which is a genetic chimera.

Cultural significance
Sheep have had associations with many cultures, especially in the Mediterranean area and Great Britain, where they form the most common type of livestock in pastoralism. Selective breeding of sheep has frequently occurred.

A wide symbology relates to sheep in ancient art, traditions and culture. In Egyptian mythology the ram was the symbol of Heryshaf. Judaism uses many sheep references including the Passover lamb. Christianity uses sheep-related images, such as: Christ as the good shepherd, or as the sacrificed Lamb of God (Agnus Dei), the bishop's Pastoral, the lion lying down with the lamb (a reference to all of creation being at peace, without suffering, predation or otherwise). Easter celebrations in Greece and Romania traditionally feature a meal of Paschal lamb. Sheep also have considerable importance in Arab culture; Eid ul-Adha is a major annual festival in Islam in which a sheep is sacrificed.

Herding sheep plays an important historico-symbolic part in the Jewish and Christian faiths, since Abraham, Isaac, Jacob, Moses, and King David all worked as shepherds.

The ram is the first sign of the Western zodiac, in which it is known as Aries. The sheep (or goat) also forms one of the animals associated with the 12-year cycle of in the Chinese zodiac, related to the Chinese calendar. Chinese tradition associates each animal with certain personality traits. See: Sheep (Zodiac).

The raising of sheep for wool and meat became a major industry in colonial Australia and New Zealand and remains significant. As a result, sheep and sheep shearing have become an important part of the folklore and cultural tradition of these two countries. In New Zealand, sheep outnumber the human population 12 to 1.

Sheep are often associated with obedience due to the widespread perception that they lack intelligence and their undoubted herd mentality, hence the pejorative connotation of the adjective 'ovine'. In George Orwell's satirical novel Animal Farm, sheep are used to represent the ignorant and uneducated masses of revolutionary Russia. The sheep are unable to be taught the subtleties of revolutionary ideology and can only be taught repetitive slogans such as "Four legs good, two legs bad" which they bleat in unison at rallies.

The rock group Pink Floyd wrote a song using sheep as a symbol for ordinary people, that is, everyone who isn't a pig or dog. People who accept overbearing governments have been pejoratively referred to as "sheeple".

In contemporary events, controversy has raged over a scientific study at the Oregon Health and Science University which, because of the unedited printing of a press-release by PETA in a British newspaper, has been accused of attempting to find a way to breed out the minority trait which causes some rams to prefer homosexual relations. Further investigation revealed it only attempts to study the genetics and circumstances which produce the phenomenon and not "cure" it.

Breeds
There are many breeds of sheep, but these are generally sub-classable as wool class, hair class and sheep meat variety breeds. Dual-purpose breeds are bred for both wool and meat.

Major wool breeds include Merino, Rambouillet, Romney, Shetland, and Lincoln. Drysdale and Herdwick are bred specifically for carpet wool.

Breeds of meat sheep include Beltex, Suffolk, Portland, Hampshire, Columbia, Texel, and Montadale.

Breeders of dual-purpose wool class sheep concentrate on fast growth, multiple births, ease of lambing and hardiness. An easy-care sheep is the Coopworth that has long wool and good lamb meat production qualities. Other dual-use breed are the Corriedale and Shropshire. Sometimes sheep are used for both purposes equally and cross-breeding is practiced to maximise both outputs. For example, Merino ewes providing wool may be crossed with Suffolk rams to produce lambs which are robust and suitable for the meat market.

Hair class sheep are the original class of sheep in the world, developed for meat and leather. They are prolific and highly resistant to disease and parasites. Dorpers and Kahtahdins are composite breeds of wool and hair crosses with different degrees of wool/hair mixes within the hair class. True hair sheep such as St. Croix, Barbados Blackbelly, Mouflon, Santa Inez and Royal White shed their protective down fiber to an all hair coat in the Spring/Summer. Hair class sheep are becoming more popular for their no-shear aspects.

Economic importance
Raising sheep was and is important to farmers in many economies, given that sheep can give milk (and its derivative products, such as cheese), wool, sheepskin (used for making clothes, footwear, rugs, and other coverings) and meat. Sheep droppings have even been sterilized and mixed with other traditional pulp materials to make paper. In the 21st century, sheep retain considerable importance in the economies of several countries. After China, the largest producers of sheep products are in the southern hemisphere: Australia, New Zealand and the Patagonian regions of Argentina, Uruguay, and Chile. Sheep play an important role in the economies of a number of smaller countries, such as Wales. In some places, like Sardinia, sheep-breeding has become the principal and characteristic activity.

In the United Kingdom, the importance of the wool trade was so significant that in the upper chamber of parliament (the House of Lords), the Lord Chancellor sits on a bench known as the Woolsack. This is, as its name suggests, a sack of wool and confers the importance of the wool trade to the English economy at the time of its installation many centuries ago.

The economic importance of sheep in much of the United States has declined as it has become, in some cases, economically unviable to ranch sheep for wool. Texas has by far the most sheep of any state, but now has only about one-tenth of the almost 11 million sheep it had in the 1940s.

In the 21st century, in some situations, sheep can provide a return on investment of up to 400% of their cost annually (including reproduction gains). Sheep breeding has played a role in several historic conflicts, such as the Scottish Highland Clearances, the American range wars, and the English "enclosing of the commons".

Domestication
Evidence for the domestication of sheep dates to 9000 BC in Iraq. DNA analysis has shown that domestic sheep are descended from two ancestor species, one of which is the mouflon. Although the second ancestor has not been identified, both the urial and argali have been ruled out. The urial (O. vignei) is found from northeastern Iran to northwestern India. It has a higher number of chromosomes (58) than domestic sheep (54) which makes it an unlikely ancestor of the latter, but it interbreeds with the mouflon. The argali sheep (O. ammon) of inner Asia (Tibet, Himalayas, Altay Mountains, Tien-Shan and Pamir) has 56 chromosomes and the Siberian snow sheep (Ovis nivicola) has 52 chromosomes.

Evidence of early domesticated sheep has been found in PPNB Jericho and Zawi Chemi Shanidar. The fleece-bearing sheep are only found since the Bronze Age. Primitive breeds, like the Scottish Soay sheep have to be plucked (a process called rooing), instead of sheared, as the kemps are still longer than the soft fleece, or the fleece must be collected from the field after it falls out. The European mouflon (O. musimon) found on Corsica and Sardinia as well as the Cretan and the extinct Cypriot wild sheep are possibly descended from early domestic sheep that turned feral.

Cuisine
Chefs and diners commonly know sheep meat prepared for food as lamb or mutton (compare the French word for "sheep": mouton).

Ewes' milk is used in the production of cheese and yogurt in many upland parts of the world. Well known sheep milk cheeses include the Roquefort of France, the brocciu of Corsica, the pecorino of Italy and the feta cheese of Greece. See Category:Sheep's-milk cheeses. Sheep milk contains lactose, and may trigger lactose intolerance in humans.

Sheep testicles - called animelles or Lamb fries in culinary terms - are considered a delicacy in many parts of the world. They are sometimes confused with Rocky Mountain oysters which are exclusively the testicles of boars or bulls.

Behavior
Some breeds of sheep exhibit a strong flocking behaviour. Flocking behaviour is advantageous to non-predatory animals; the strongest animals fight their way to the center of the flock[dubious ??? discuss] which offers them great protection from predators. It can be disadvantageous when food sources are limited and sheep are almost as prone to overgrazing a pasture as goats. In Iceland, where sheep have no natural predators, and grasses grow slowly, none of the various breeds of sheep exhibit a strong flocking behaviour.

Sheep flocking behaviour is so prevalent in some English breeds that special names apply to the different roles sheep play in a flock. One calls a sheep that roams furthest away from the others an outlier, this sheep ventures further away from the safety of the flock to graze, due to a larger flight zone or a weakness that prevents it from obtaining enough forage when with the flock, while taking a chance that a predator, such as a wolf, will attack it first because of its isolation.

Another sheep, the bellwether, which never goes first but always follows an outlier, signals to the others that they may follow in safety. When it moves, the others will also move. Traditionally this was a castrated ram (or wether) with a bell hung off a string around its neck. The tendency to act as an outlier, bellwether or to fight for the middle of the flock stays with sheep throughout their adulthood; that is unless they have a scary experience which causes them to increase their flight zone.

According to a spokesperson of the British National Sheep Association, "Sheep are quite intelligent creatures and have more brainpower than people are willing to give them credit for." For example, sheep in Yorkshire, England found a way to get over cattle grids by rolling on their backs. A study published in National Geographic (December 8) showed a sheep can remember the faces of fifty other sheep for over two years. If sheep are acting poorly, they are known as a "Goulden in the rough."

Sheep can become hefted to one particular pasture so they do not roam far from home. Since the outbreak of foot and mouth disease in the United Kingdom, transplanted sheep have had to be trained to stay in their grazing area.

Sheep are also one of the many animals that can display a preference for homosexuality and are one of the few in which this occurrence has been systematically studied. It occurs in about eight percent of rams on average. Its occurrence does not seem to be related to dominance or flock hierarchy; rather the rams typical motor pattern for intercourse is merely directed at rams instead of ewes.

Sheep have horizontal slit shaped pupils. The narrower the pupil, the more accurate the depth perception of peripheral vision is; so narrowing it in one direction would increase depth perception in that plane. Animals like goats and sheep may have evolved horizontal pupils because better vision in the vertical plane may be beneficial in mountainous environments.

Glossary
This is a glossary of terms that relate to sheep and domestic sheep. Note that some terms have localised meanings, and may be used only in one geographical region, or may mean slightly different things in different areas.

Cryptorchid ??? a male sheep with no descended testicles, with them both being retained internally.
Ewe ??? a female sheep, capable of producing lambs.
Hoggett (or Hoggatt) ??? a sheep which by virtue of its age and development is no longer a lamb, but not yet mutton. esp. in relation to meat breeds.
Lamb ??? a young sheep, generally unweaned. In many Eastern countries, there is a less strict definition of lamb which may include older hoggetts. Also used to refer specifically to the meat of such a sheep.
Monorchid ??? a male sheep that has only one descended testicle, with the other being retained internally. They are less fertile but have an increased production of lean meat due to the presence of testosterone.
Mutton ??? an older female sheep to be used for meat. Also used to refer specifically to the meat of such a sheep. May refer to goat meat in eastern countries. Derived from the French word Mouton (sheep).
Ram (also called a tup) ??? an uncastrated male sheep.
Riggwelter ??? a sheep that has fallen onto its back and (usually because of the weight of its fleece) is unable to get back up.
Old-season lamb ??? a lamb a year old or more.
Ovine ??? member of the genus Ovis.
Slink ??? a very young lamb.
Sucker ??? an unweaned lamb.
Teg ??? a sheep in its second year.
Wether ??? a castrated male sheep.

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