the Origin of Modern Horse Breeds

Horses come in various sizes and shapes. The draft breeds can top 20 hands (80 inches, 2 metres) while the smallest miniature horses can stand as low as 5.2 hands (22 inches, 0.56 metres). The Patagonian Fallabella, usually considered the smallest horse in the world, compares in size to a German Shepherd Dog.

Several schools of thought exist to explain how this range of size and shape came about. These schools grew up reasoning from the type of dentition and from the horses' outward appearance. One school, which we can call the "Four Foundations", suggests that the modern horse evolved from two types of early domesticated pony and two types of early domesticated horse; the differences between these types account for the differences in type of the modern breeds. A second school -- the "Single Foundation" -- holds only one breed of horse underwent domestication, and it diverged in form after domestication through human selective breeding (or in the case of feral horses, through ecological pressures). Finally, certain geneticists have started evaluating the DNA and mitochondrial DNA to construct family trees. See: Domestication of the horse

Breeds, studbooks, purebreds and landraces
Selective breeding of horses has occurred as long as man has domesticated them. However, the concept of controlled breed registries has gained much wider importance during the 20th century. One of the earliest formal registries was General Stud Book for thoroughbreds, a process that started in 1791 tracing back to the foundation sires for that breed. These sires were Arabians, brought to England from the Middle East.

The Arabs had a reputation for breeding their prize mares to only the most worthy stallions, and kept extensive pedigrees of their "asil" (purebred) horses. During the late middle ages the Carthusian monks of southern Spain, themselves forbidden to ride, bred horses which nobles throughout Europe prized; the lineage survives to this day in the Andalusian horse or caballo de pura raza español.

The modern landscape of breed designation presents a complicated picture. Some breeds have closed studbooks; a registered Thoroughbred, Arabian, or Quarter Horse must have two registered parents of the same breed, and no other criteria for registration apply. Other breeds tolerate limited infusions from other breeds—the modern Appaloosa for instance must have at least one Appaloosa parent but may also have a Quarter Horse, Thoroughbred, or Arabian parent and must also exhibit spotted coloration to gain full registration. Still other breeds, such as most of the warmblood sporthorses, require individual judging of an individual animal's quality before registration or breeding approval.

Breed registries also differ as to their acceptance or rejection of breeding technology. For example, all (Jockey Club) Thoroughbred registries require that a registered Thoroughbred be a product of a natural mating ('live cover' in horse parlance). A foal born of two Thoroughbred parents, but by means of artificial insemination, is barred from the Thoroughbred studbook. Any Thoroughbred bred outside of these contraints can become part of the Performance Horse Registry.

Many breed registries allow artificial insemination (AI), embryo transfer, or both. The high value of breed stallions has helped with the acceptance of these techniques because they 1.) allow for more doses with each stallion 'collection' and 2.) take away the risk of injury during breeding.

Hotbloods, Warmbloods, and Coldbloods
The Arabian horses, whether originating on the Arabian peninsula or from the European studs (breeding establishments) of the 18th and 19th centuries, gained the title of "hotbloods", for their temperament. Arabians are known and valued for their sensitivity, keen awareness, athleticism, and energy. It was these traits, combined with the lighter aesthetically refined bone structure which was used as the foundation of the Thoroughbreds. They wished to infuse some of this energy and athleticism into their own best cavalry horses.

The Thoroughbred is unique to all breeds in that its muscles can be trained for either fast-twitch (for sprinting) or slow-twitch (for endurance) making them an extremely versatile breed. Arabians are used in the sport horse world almost exclusively for endurance competitions. Breeders continue to use Arabian sires with Thoroughbred mares to enhance the sensitivity of the offspring for use in equestrian sports. An Arabian/Thoroughbred cross is known as an Anglo-Arabian. Horsed in this group are commonly called 'hotbloods.'

True hotbloods usually offer greater riding challenges and rewards than other horses. Their sensitivity and intelligence enable quick learning, and greater communication and cooperation with their riders. However, they can sometimes also decide that new flowerpot is really a dragon, and you will spend the next five minutes calming them down.

Muscular and heavy draft horses are more or less known as "coldbloods", as they have been bred to be workhorses and carriage horses with calm temperaments. Harnessing a horse to a carriage requires some level of trust in the horse to remain calm when restrained. The best known coldbloods would probably be the Budweiser Clydesdales.

Warmblood breeds began in much the same way as the Thoroughbred. The best of their carriage or cavalry horses were bred to Arabian, Anglo-Arabian and Thoroughbred sires. The term "warmbloods" is sometimes used to mean any draft/Thoroughbred cross although this is becoming less common. The warmblood name has become the term to specifically refer to the sporthorse breed registries than began in Europe, although now worldwide. These registries, or societies, such as the Hanoverian, Oldenburg, Trakkhener, and Holsteiner have dominated the Olympics and World Equestrian Games in Dressage and Show Jumping since the 1950s.