The Dorset or Dorset Horned breed of sheep is known mostly for its prolific lambing. It has been known to produce two lambing seasons per year: bred in May for lambs finished by the holidays, and bred again immediately after the first lambing to produce again in March or April. This type of management, the ewes sold with the lambs, sometimes produces as many as four or five lambs a year.
The Dorset is an ancient breed likely developed from white faced, horned, short wooled sheep that thrived in the sheltered valleys and lush hill pastures of southwestern England. Today, the Dorset is globally distributed and found in two varieties, Horned and Polled. The Dorset Horn (or Horned Dorset) is of conservation interest.
Dorsets are white sheep with open faces and long bodies. Ewes weigh 150–200 pounds, and rams weigh 225–275 pounds. The sheep are avid grazers and use feed well. Ewes are heavy milkers, easily able to raise their own lambs. They have also been used in dairying. Dorset sheep produce between five and nine pounds of medium grade wool per year. In the Horn variety, both ewes and rams carry horns. Ewes’ horns are light, curving forward neatly; rams’ horns are heavy and spiral out as well as curving forward.
The single most important attribute of the Dorset is its extended breeding season, also called nonseasonal or aseasonal breeding. This characteristic, not found in any other British breed, is an important performance trait. Sheep of most breeds are seasonal breeders, mating in the fall and producing lambs in the spring. In contrast, Dorsets can be bred in the spring for production of lambs in the fall. Some ewes will raise two sets of lambs a year, with multiple births not uncommon. Dorsets tolerate heat well, and heat tolerance contributes to Dorset rams’ ability to breed earlier in the season than rams of other breeds.
The first Horned Dorsets were brought to the United States in 1885. In 1948, a dominant gene for polledness occurred resulting in Polled Dorsets which are now popular in the farm flock states. Dorset ewes are prolific, heavy milkers that produce lambs with moderate growth and maturity that yield heavy muscled carcasses.