Although most people picture a Siberian husky or a Malamute when they think of sled dog racing, the dog which is bred and used by mushers is a landrace breed. "Landrace" breeds arise naturally, out of the needs of their breeders. You could call it a kind of "purpose-built mutt."
The landrace used in mushing is called a "husky," although it is smaller and trimmer than most husky breeds. It comes in a variety of coat and eye colors, and is bred for speed, endurance, and "easy keeping," meaning that it can go far on a minimum amount of food.