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Appendix Quarter Horses Breed Description

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Breed Organization

American Quarter Horse Association AQHA

American Appendix Horse Association AAHA

Native Country
United States Of America

Other Names

Adult Height

Adult Weight

General Description

Appendix Horse: - A horse registered with AQHA which is the result of breeding a Thoroughbred and an American Quarter Horse that has a permanent number, or a combination of an Appendix numbered American Quarter Horse and an American Quarter Horse with a permanent number. Appendix horses are distinguished by an "X" in front of their registration number and their certificates are gold.

There are three different mixes of horses that are eligible to be registered in AQHA's registry:

1. Registered Appendix (X) + Registered American Quarter Horse (QH) ' Registered Appendix foal(X)
2. Registered American Quarter Horse (QH) + Registered American Quarter Horse (QH) ' Registered American Quarter Horse foal (QH)
3. Recognized Thoroughbred (TB) + Registered American Quarter Horse (QH) ' Registered Appendix foal (X)

Colors of Horses
There are 13 recognized colors for American Quarter Horses. Bay, Black, Brown, Sorrel, Chestnut, Dun, Buckskin, Red Dun, Grullo, Palomino, Gray, Red Roan, Blue Roan.

Bay: Body color ranging from tan, through red, to reddish brown; mane and tail black; usually black on lower legs.
Black: Body color true black without light areas; mane and tail black.
Brown: Body color brown or black with light areas at muzzle, eyes, flank, and inside upper legs; mane and tail black.
Sorrel: Body color reddish or copper-red; mane and tail usually same color as body, but may be flaxen. The most common color of American Quarter Horses.
Chestnut: Body color dark red or brownish-red; mane and tail usually dark red or brownish-red but may be flaxen.
Dun: Body color yellowish or gold; mane and tail may be black, brown, red, yellow, white or mixed; often has dorsal stripe, zebra stripes on legs, transverse over withers.
Buckskin: Body color yellowish or gold; mane and tail black; usually black on lower legs.
Red Dun: A form of dun with body color yellowish or flesh colored; mane, tail and dorsal stripe are red.
Grullo: Body color smoky or mouse-colored (not a mixture of black and white hairs, but each hair mouse-colored.) ; mane and tail black; usually black on the lower legs; often has dorsal stripe.
Palomino: Body color golden yellow, mane and tail white. Palominos typically do not have dorsal stripes.
Gray: Body color a mixture of white with any other colored hairs; often born solid-colored or almost solid-colored and gets lighter with age as more white hairs appear.
Red Roan: More or less uniform mixture of white with red hairs on the body, but usually darker on head and lower legs; can have red, black, or flaxen mane and/or tail.
Blue Roan: More or less a uniform mixture of white with black hairs on the body, but usually darker on head and lower legs; can have a few red hairs in mixture.

AAHA allows the horse breeder to take the Thoroughbred horse, the Quarter Horse or Paint and make the Appendix breed. Breeding Stock Paints are welcome to dual register without any prejudice to lack of color, or the Paint with Thoroughbred in their bloodline may dual register without prejudice to having color. The coded appendix horse in the American Quarter Horse Association is welcome to register in as the Appendix breed of horse. Allowing the owner to breed this horse to other horses and keep the pedigree ongoing.

AAHA has an Enrollment program for horse owners of Quarter Horse, Paints and Thoroughbred to enroll their horse's pedigree in AAHA, so that the offspring of these horses are eligible for Registration into AAHA as an Appendix breed. If you have a stallion this will give you more revenue because you can offer mare owners breeding certificate to register in AAHA. You may breed your Quarter Horse to a Paint, Thoroughbred or another Appendix or coded appendix with AQHA and offer the owner a way to register the foal. A Paint or Thoroughbred stallion owner may also do the same thing.


Since the American Quarter Horse formally established itself as a breed, the AQHA stud book has remained open to additional Thoroughbred blood via a performance standard. An "Appendix" American Quarter Horse is a first generation cross between a registered Thoroughbred and an American Quarter Horse or a cross between a "numbered" American Quarter Horse and an "appendix" American Quarter Horse. The resulting offspring is registered in the "appendix" of the American Quarter Horse Association's studbook, hence the nickname. Horses listed in the appendix may be entered in competition, but offspring are not initially eligible for full AQHA registration. If the Appendix horse meets certain conformational criteria and is shown or raced successfully in sanctioned AQHA events, the horse can earn its way from the appendix into the permanent studbook, making its offspring eligible for AQHA registration.

Since Quarter Horse/Thoroughbred crosses continue to enter the official registry of the American Quarter Horse breed, this creates a continual gene flow from the Thoroughbred breed into the American Quarter Horse breed, which has altered many of the characteristics that typified the breed in the early years of its formation. Some breeders, who argue that the continued infusion of Thoroughbred bloodlines is beginning to compromise the integrity of the breed standard, favor the earlier style of horse, have created several separate organizations to promote and register "Foundation" Quarter Horses.


Dependant on use.


Racing, trail riding (endurance, pleasure, mileage/hourly or working ranch), hunter/jumper, dressage, cutting, ranch work or horse racing.


Hyperkalemic periodic paralysis (HYPP), which is caused by an autosomal dominant gene linked to the stallion Impressive. It is characterized by uncontrollable muscle twitching and substantial muscle weakness or paralysis among affected horses. Because it is a dominant gene, only one parent has to have the gene for it to be transmitted to offspring. There is a DNA test for HYPP, the AQHA requires testing and is now limiting registration of some horses who possess the gene.

Hereditary Equine Regional Dermal Asthenia (HERDA), also known as hyperelastosis cutis (HC). This is caused by a recessive gene, and thus, unlike HYPP, HERDA can only be transmitted if both parents carry the gene. When a horse has this disease, there is a collagen defect that results in the layers of skin not being held firmly together. Thus, when the horse is ridden under saddle or suffers trauma to the skin, the outer layer often splits or separates from the deeper layer, or it can tear off completely. It rarely heals without disfiguring scars. Sunburn can also be a concern. In dramatic cases, the skin can split along the back and even roll down the sides, with the horse literally being skinned alive. Most horses with HERDA are euthanized for humane reasons between the age of two and four years. The very hotly debated and controversial theory, put forth by researchers at Cornell University and Mississippi State University is that the sire line of the great foundation stallion Poco Bueno is implicated as the origin of the disease. There currently is no DNA test for HERDA, but active research is ongoing to try and pinpoint the gene.

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