Its chief distinction is its horns – large and curled – in both rams and ewes. Ewes with horns of this size and type are unique to the Dorset breed among modern domestic sheep, while the rams’ horns are even larger and tightly curled in “regimental mascot” style.
The Dorset Horn is a big sheep, hardy and very active. It boasts a capacious stomach and is an excellent “doer”; a ewe in good condition tends always to look as though she is in lamb and even the rams often look gravid. The fleece is of medium length, fine and very white, and the face and legs, clear of wool, are also noticeably white and show another of the Dorset Horn’s distinguishing features – a pink nose and light coloured hooves. This pink and white look is particularly marked in lambs where it appears to be intensified. A young Dorset has "hoofs of mother-of-pearl and a nose like a fresh raspberry".
The Dorset’s characteristics, the horns and the breeding rate, were bequeathed to it by a dominant ancestor – the now extremely rare Portland Sheep, found originally on and near Portland Island, very close to Dorchester. The Portland Sheep was first recorded in the sixteenth century and its origin is obscure, but it was spectacularly horned, and noteworthy because of its ability to lamb all year round – with up to four births in two years.