Extracts from the book "All about the Working Border Collie" by Marjorie Quarton...
The Duke of Gordon mated his setter with a collie bitch because she was good at pointing game and gathering sheep.....mottled coloring of some Border Collies reflects the sign of a mixed ancestry. Around 1934 a farmer with a good working Border Collie mated her on two occasions with a liver and white spaniel of cocker type. Border Collies can sometimes look as if they were half setter or half pointer when there is no possibility of this being the case.
We have owned at different times four dogs by the classically bred Border Collie Glenabo Lad, but from unrelated mothers. These dogs were brown, white and mottled, with large low-set ears, strong jaws and domed skulls. The sire was a black and white dog with bent over ears, wedge shaped head and no mixed ancestry. None of the three bitches responsible for the four dogs was in any way unusual to look at. These brown dogs all had more 'eye' than either parent. There was no brown dog in their pedigrees nearer than five generations back.
There are two distinct types of brown sheep dog, the foxy-red and the liver coated. The liver colour is often associated with a distinctive trotting gait, in which the hocks are scarcely bent, and the whole hind leg swings foward. I have noticed pointers and Irish setters trotting like this.
Extract from National Dog Jan 2001 Origins based on a mixed ancestry?
"... mixed ancestry included the Bearded Collie, the Harlequin Collie and the Bob-tailed Sheepdog. There is also evidence which points to Setter bloodlines...."
Could this be why there is the different colored Border Collies, spotted muzzles, jowelness, erect or floppy ears, coat length, coat texture, gait, dog type and standard vary ? Purebred Dogs into the Twenty First Century A must read if you are concerned about the genetic health of our dogs.