Breed Profile: American Quarter Horse

During summer camp (or winter camp, or spring camp) the kids learn about horse breeds and colors. This is one of my favorite lectures to teach because I’m a bit of a nerd when it comes to color genetics and breed histories. The kids seem to enjoy it as well, mostly because at the end we walk through the barn and they point at every single horse we pass and ask, “what breed is that!!?”

I encourage them to figure it out on their own, and they’re usually 60/40 on their answers. The most common answer by far is Quarter Horse (or QH cross). Some of our most beloved school horses like Sugar and Puzzle belong to this breed, which is the most popular breed in the United States, so here’s the story of these wonderful, versatile horses.

The Quarter Horse is a uniquely American breed. In the 17th century colonists crossed English Thoroughbreds with some of the horses used by Native Americans, which were largely ofIberian or Spanish descent. The most notable Quarter Horse ancestor is a Thoroughbred named Janus, who was a grandson of the Godolphin Arabian.janus

(More on the history of the Thoroughbred.)

The combination of swift Thoroughbreds and hardy native horses resulted in a strong, stocky horse that could hold a blistering pace over a quarter mile. The Quarter horse was sometimes called, “The Famous American Quarter Running Horse,” and while they were used for farm work during the week these horses excelled in weekend races over short dirt tracks, often beating their Thoroughbred competitors.

Quarter Horses found an additional calling in the 19th century. Pioneers needed a strong, reliable horse to carry them across the untamed wilderness as they headed West. They crossed their Quarter Horses with Mustangs and horses from local Native American tribes and discovered that the resulting foals had an innate “cow sense” which made them ideal for working on ranches.


Westward expansion also sparked the creation of rodeos, which began as places for riders to showcase their horses’ working ability. Quarter Horses dominated the rodeo rings, and today they are still the preferred mounts for events such as reining, barrel racing, cow cutting, and bronc riding. In the 1940s the first breed registry formed and the American Quarter Horse Association began to unite the proud owners and breeders of these influential horses.


The Quarter Horse breed registry recognizes two types of horses, Foundation and Appendix. Foundation Quarter Horses are horses with no Thoroughbred blood aside from that which was initially used to create the breed. However, the relationship between Thoroughbreds and Quarter horses has persisted throughout the years and the books remain open to new Thoroughbred blood so crosses are common. An Appendix quarter horse is either a cross between a Foundation horse and a Thoroughbred or a Foundation and another Appendix. These horses are listed in the appendix of the stud books and are allowed to compete in AQHA sanctioned competitions but their offspring may not be permitted full AQHA registration.

Unfortunately, Quarter Horses are also prone to breed specific diseases such as Hyperkalemic Periodic Paralysis and Equine Polysaccharide Storage Myopathy.

. Hyperkalemic Periodic Paralysis (HYPP) – Is caused by a genetic mutation that only affects horses with the popular stallion Impressive in their pedigree. It creates problems related to the release of sodium to the muscles, which can result in spasms, cramps, and paralysis that can last for hours. It is possible for horses to die during a HYPP attack due to heart or respiratory failure, but some horses only ever experience mild symptoms like muscle tremors on their neck, shoulder, and flank. HYPP is a dominant gene, which means that horses only need one copy of the mutation to be affected. There is no cure for HYPP but it can be managed. Horses who are kept on regular feed schedules, drink lots of water, and have adequate access to grass or forage tend to have fewer attacks.


. Equine Polysaccharide Storage Myopathy (EPSM or PPSM) –  This is a glycogen storage disease, which means it disrupts the process of glycogen being absorbed and used as energy for the body. Horses with PPSM may appear normal when resting, but will exhibit symptoms like stiffness, shortness of stride, muscle tremors, sweating, or lameness when in work. This happens because the horses glycogen levels get used up much faster than a normal horse’s, so their muscles become deprived very easily. At its worst, PPSM can cause painful muscle cramps or weakness, which renders horses unable to stand, and may result in colic. There is no cure, but PPSM can be managed through a special, low-starch, high-fat diet and by slowly increasing the amount a horse exercises.  

Most horses are not affected by these diseases, and today the AQHA has over 2 million horses registered across the world.

Modern Quarter Horses compete in virtually any event, from rodeo, to western pleasure, to hunters, jumpers, and Dressage. They are generally stocky, with compact builds and heavy muscling in their neck, shoulders, and hindquarters. They tend to have large cheeks, narrow muzzles, and small, fine ears. They are known for their versatility and even temperament, which also makes them excellent school horses. (However, every horse is an individual and may have varied temperaments.)

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Do you have a favorite Quarter Horse? Can you guess who else in the barn is a Quarter Horse? Let us know in the comments below, or on Facebook or Twitter.

Until next time, happy riding!

Featured image is by Taylor Crass Photography.

Other images belong to,, the National Cowgirl Museum,,, and


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