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Polled Dorset
The Polled Dorset is a breed of sheep developed for meat at the North Carolina State University Small Ruminant Unit in 1956. The name refers to the fact that it is a hornless variation of the Horned Dorset breed. The Polled Dorset is the result of a genetic mutation by which some of the offspring of a certain ram grew no horns. After some years of breeding work, a strain of Dorset was developed which had lost the characteristic horns and which bred true.
Polled Dorsets are an all-white, medium-sized sheep, prolific and able to breed out of season. The carcases are muscular with good conformation and the adults produce a thick fleece, which is free from dark fibers. Since its development, the number of Polled Dorsets registered in the United States has grown to exceed the number of Horned Dorsets. Without horns the sheep are easier to handle and there is much less risk of the rams hurting themselves or others by butting. The Polled Dorset is sometimes confused with the Australian Poll Dorset, but that breed did not start as a genetic mutation but resulted from the introduction of Corriedale and Ryeland blood into the Dorset breeding program.
==History==
In 1949, four hornless lambs were sired from a Horned Dorset on a farm at North Carolina State University in Raleigh, North Carolina. 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 the Horned Dorset. Eventually, a ewe gave birth to twin rams. NCSU 401 was a regular horned Dorset, but his brother, "NCSU 402", was born polled, without horns, due to a genetic mutation. Thus, the Polled Dorset was born. NCSU 402 was the official name given to the first true Polled Dorset sheep. It was named in accordance with the naming system that has been used at the NCSU Small Ruminant Unit since it started its breeding program.
After research and testing were done to confirm that the Polled Dorset carried the same characteristics as the Horned Dorset and was able to pass on these traits, the Continental Dorset Club, formed in 1898, registered the very first Polled Dorset sheep in 1956.〔 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 were 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.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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