Members of a breed share a similar ancestry and bloodlines, which make their physical characteristics and behavioral traits more predictable. For example, Thoroughbreds are bred to run fast. Clydesdales, the famous Budweiser beer horses, are draft animals bred to be big and strong enough to pull heavy loads. Purebreds are registered with an association that represents and promotes their breed. They are often purchased and bred based on their pedigrees, the papers that historically document their bloodlines. Unregistered horses that have no documented parentage are referred to as “grade” horses.