Dorper

A flock of sheep of the breed Dorper (DORset Horn + Blackhead PERsian) is s seen in the first episode of the seventh season.

Appearance & History
Notice how they have white bodies but black heads and faces. This breed was developed in South Africa in the 1930s by crossing the Dorset Horn with the Blackhead Persian sheep.

Source

 * 1) Blog Whisperer's blog post from May 16