The British Milk Sheep (BMS) is a composite breed, medium to large in size. They are said to be a 'dairy breed' as they produce a sustained milk yield over and above that needed to rear their lambs, usually triplets.
There is conflicting information on the composition of the breed but the problem seems to be with the percentages that the East Friesian, West Friesian, Blue-faced Leister, Polled Dorset and Lleyn contributed to the British Milk Sheep. Sources do agree that Laurent Alderson developed the breed in the Wiltshire and Northumberland area.
The breed was released in 1980. It is Britain's most prolific breed with mature ewes averaging 3.07 lambs and yearlings 2.21 lambs per ewe. An especially broad pelvic area aids easy lambing. The lambs are generally of good weight – from eight to ten pounds – and will grow to over 100lbs, producing succulent, lean meat with little or no fat.
A 300 day lactation may produce a milk yield of 650 – 900 litres. Milk solids are high and protein content rises throughout the lactation period, as does the fat content. Triplet lambs gain 0.33kg per day in weight. The high fat content (starting around 5.5% at the beginning of the lactation period and rising to around 9%) makes the milk excellent for cheese-making. The output of cheese from these ewes is nearly twice that of cows' milk.