Is a foal born to two American Quarter Horses that has big white spots on its body an American Quarter Horse? Traditionally, the answer was no, but in 2004, AQHA?s ?excessive white? rule was rescinded, allowing horses with these markings to be registered. Any horse with excessive white ? see Rule 205(d) in the AQHA Handbook ? will have a notation on its registration certificate saying ?This horse has white markings designated under AQHA rules as an undesirable trait and uncharacteristic of the breed.?
The only pinto pattern known to exist in American Quarter Horses is the overo (oh VEHR-oh) pattern. This includes subpatterns splash and sabino. The other pinto patterns, tobiano and tovero (a mix of tobiano and overo) have yet to be discovered in the Quarter Horse breed.
Overo most commonly describes frame, which is a coloration that looks like a frame of color surrounding a patch of white. Horses with this pattern usually have white on the face and at least one dark leg. The white on the horse's body rarely crosses over the horse's spine, and the spots are usually fairly jagged.
Splash white horses look as if they were picked up and dipped in white paint. The white begins at the bottom (legs and lips) and moves upward. The markings can vary from normal markings (sometimes as little as just a snip) to much more extensive markings. Markings are usually crisp with smooth edges, and blue eyes are very common.
A master of disguise, sabino (sah-BEE-no) produces an extremely variable amount of white spotting from normal socks to wildly colored pintos. Its most common characteristics include markings on the face from snip to bald face, almost always accompanied by a white spot on the lower lip or chin; leg white; and roan hairs interspersed in the coat. The roaning is not necessarily evenly spread over the horse's body. Sabino differs from true roan by the amount of white ? true roans are dark only on their head and legs. It is also different from a rabicano, as the latter always affects the tailhead, producing the ?skunk tail? effect.
Patches of white on the leg (especially the knee) unconnected to white markings is another sabino trait.
In its most minimal form, sabino presents itself as a set of normal-height white socks and white on the face - markings so minimal one would never think the horse could produce pinto when crossed with the right mate.
Early directors of AQHA and old-time horsemen thought paint markings were a sign of mongrel breeding, thus prompting them to exclude such horses from the registry.
A foal from two American Quarter Horses that shows undesirable white must be parentage-verified through DNA typing.
Breeding two overo horses can cause a recessive trait called Lethal White Syndrome. This is an all-white foal that is born with intestinal tract abnormalities and dies shortly thereafter. If a breeder crosses two frame overo horses that are heterozygous carriers, there is a 25 percent chance of producing a lethal white foal (homozygous carrier). If an overo carrier is bred to an unaffected horse, there is no possibility of producing a lethal white. The University of California-Davis has a test available to determine if a horse is a carrier.
The 1961 Rondo Leo stallion Mr Gunsmoke was famous for siring horses with sabino characteristics. He is the sire of National Reining Horse Association Hall of Famer Hollywood Smoke and grandsire of famous reining stallion Trashadeous.