The American Quarter Horse is an American breed of horse that excels at sprinting short distances. Its name came from its ability to outdistance other horse breeds in races of a quarter mile or less.
In the 17th century, colonists on the eastern seaboard of what today is the United States began to cross imported English Thoroughbred horses with assorted “native” horses such as the Chickasaw horse, which was a breed developed by Native American people from horses descended from Spain, developed from Iberian, Arabian and Barb stock brought to what is now the Southeastern United States by the Conquistadors.
One of the most famous of these early imports was Janus, a Thoroughbred who was the grandson of the Godolphin Arabian. He was foaled in 1746, and imported to colonial Virginia in 1756. The influence of Thoroughbreds like Janus contributed genes crucial to the development of the colonial “Quarter Horse”. The breed is sometimes referred to as the “Famous American Quarter Running Horse”. The resulting horse was small, hardy, and quick, and was used as a work horse during the week and a race horse on the weekends.
As flat racing became popular with the colonists, the Quarter Horse gained even more popularity as a sprinter over courses that, by necessity, were shorter than the classic racecourses of England, and were often no more than a straight stretch of road or flat piece of open land. When matched against a Thoroughbred, local sprinters often won. As the Thoroughbred breed became established in America, many colonial Quarter Horses were included in the original American stud books, starting a long association between the Thoroughbred breed and what would later become officially known as the “Quarter Horse,” named after the 1⁄4 mile (0.40 km) race distance at which it excelled.
The modern Quarter Horse has a small, short, refined head with a straight profile, and a strong, well-muscled body, featuring a broad chest and powerful, rounded hindquarters.
There are two main body types: the stock type and the hunter or racing type. The stock horse type is shorter, more compact, stocky and well muscled, yet agile. The racing and hunter type Quarter Horses are somewhat taller and smoother muscled than the stock type, more closely resembling the Thoroughbred.
This breed is subject to more health issues than other breeds. With 5 known breed-specific health issues, owners have to watch out for equine polysaccharide storage myopathy (EPSM/PSSM), glycogen branching enzyme deficiency (GBED), hereditary equine regional dermal asthenia (HERDA), hyperkalemic periodic paralysis (HYPP), and lethal white syndrome.