The Polled Dorset is an American breed of

domestic sheep Sheep or domestic sheep (''Ovis aries'') are domesticated, ruminant mammals typically kept as livestock. Although the term ''sheep'' can apply to other species in the genus '' Ovis'', in everyday usage it almost always refers to domesticated ...

. It is a polled (hornless) variant of the British

Dorset Horn The Dorset Horn is an endangered British breed of domestic sheep. It is documented from the seventeenth century, and is highly prolific, sometimes producing two lambing seasons per year. Among British sheep, it is the only breed capable of bre ...

. It was developed at the North Carolina State University Small Ruminant Unit in the 1950s after a

genetic mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, ...

led to the birth of a polled ram. After some years of breeding work, a true-breeding polled strain was established. It is an all-white sheep of medium size, prolific and able to breed out of season. The carcass is muscular with good conformation, and the fleece is free from dark fiber. The number of Polled Dorsets registered in the United States has grown to exceed the number of Horned Dorsets.

History

In 1949, four hornless lambs were sired by a Horned Dorset on a farm at North Carolina State University in

Raleigh Raleigh (; ) is the capital city of the state of North Carolina and the seat of Wake County in the United States. It is the second-most populous city in North Carolina, after Charlotte. Raleigh is the tenth-most populous city in the Southeas ...

. Over the next five years, as part of their normal breeding program, those four ewes and the other ewes on the farm were bred to a Horned Dorset ram. Eventually, a ewe gave birth to twin rams: one was normally horned, but the other, NCSU 402, was polled. From 1956 the Polled Dorset was registered by the Continental Dorset Club (started in 1898), in the same flock book as the Dorset Horn. Livestock scientists, the late Dr. Lemuel Goode and the late Sam Buchanan, are credited with identifying and developing the hornless sheep. The offspring of NCSU 402 were bought by other breeders, and within twenty years seventy percent of all registered Dorsets were polled. The success of the Polled Dorset has made it considered to be the second most popular sheep breed in the United States. A polled strain of Dorsets was also developed in Australia in the 1900s; however, these were not as a result of a genetic mutation but resulted from the introduction of Corriedale and Ryeland blood into the Dorset Horn.

Conformation

Polled dorsets at the North Carolina State University small ruminant group farm

The Polled Dorset is a medium-sized sheep, long-lived and prolific, and a heavy milker. It produces hardy lambs with moderate growth and maturity that yield heavily muscled carcasses. Their fleece is very white, strong, close, free from dark fiber and extends down the legs. When

shorn Sheep shearing is the process by which the woollen fleece of a sheep is cut off. The person who removes the sheep's wool is called a '' shearer''. Typically each adult sheep is shorn once each year (a sheep may be said to have been "shorn" or ...

, fleece averages between in ewes, and fifty to seventy percent of their fleece can be used. The staple length ranges from with a numeric count of 46's-58's. The fiber diameter ranges from 27.0 to 33.0 microns. At maturity, ewes weigh between , some weighing more in show condition. Mature rams range in weight from . Dorsets are noted for their ability to be bred more than once per year and are commonly used in

crossbreed A crossbreed is an organism with purebred parents of two different breeds, varieties, or populations. ''Crossbreeding'', sometimes called "designer crossbreeding", is the process of breeding such an organism, While crossbreeding is used to mai ...

ing to produce females for out-of-season breeding. They are one of the few breeds that have this characteristic. Multiple births are common, and they work well in commercial operations, including programs where rams are specifically used to sire lambs for slaughter. These rams are known as terminal sires since their genetics are more suitable for slaughter than breeding purposes. Since the breed first became commercial, it has spread to

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

and become a major contributor in the commercial lamb industry. The breed adapts well to confinement and is readily used in accelerated crossbreeding programs. Polled Dorsets thrive under grass-based and feedlot conditions and are more suitable on small farms that are intensely managed.

History

Conformation

References

Further reading