BREEDING THOROUGHBRED RACE HORSES

Horse breeding refers to reproduction of horses, and particularly the human-directed process of selective breeding of animals, particularly purebred horses of a given breed. While feral and wild horses breed successfully without human assistance, planned matings can be used to produce specifically desired characteristics in domesticated horses. Furthermore, modern breeding management and technologies can increase the rate of conception, a healthy pregnancy, and successful foaling.

The male parent of a horse, a stallion, is commonly known as the sire and the female parent, the mare, is called the dam. Both are genetically important, as each parent provides half of the genetic makeup of the ensuing offspring, called a foal. (Contrary to popular misuse, the word "colt" refers to a young male horse only; "filly" is a young female.) Though many amateur horse owners may simply breed a family mare to a local stallion in order to produce a companion animal, most professional breeders use selective breeding to produce individuals of a given phenotype, or horse breed. Alternatively, a horse breeder could, using individuals of differing phenotypes, create a new horse breed with specific characteristics.
Some horse breeders consider the quality of the sire to be more important than the quality of the dam. However, other breeders maintain that the mare is the most important parent. Because stallions can produce far more offspring than mares, a single stallion can have a greater overall impact on a breed. However, the mare may have a greater influence on an individual foal because its physical characteristics influence the developing foal in the womb and the foal also learns habits from its dam when young. Foals may also learn the "language of intimidation and submission" from their dam, and this imprinting may affect the foal's status and rank within the herd. Many times, a mature horse will achieve status in a herd similar to that of its dam; the offspring of dominant mares become dominant themselves.
The Thoroughbred remains one of the most important breeds used in modern horse breeding. They have been incredibly influential on many of the favorite breeds of today, including the American Quarter Horse, the Morgan (a breed that went on to influence many of the gaited breeds in America), the Standardbred, and others. Along with the Arabian, the Thoroughbred continues to be a favorite as an improver of breeds. This is most notable in the Warmblood breeds, which occasionally infuse the hotter, leaner Thoroughbred blood when needed.
While the Thoroughbred is sometimes referred to as a “purebred”, it is really a single breed itself, rather than the avatar of all horse breeds. Like all breeds, the Thoroughbred has distinct characteristics that define its beauty and worth, such as a well chiseled head on a long neck, high withers, a deep chest, a short back, good depth of hindquarters, a lean body, and long legs. Thoroughbreds are also praised for their great speed, temperament and appearance. They have large expressive eyes, long legs and very thin skin, allowing us to see the vessels and muscles. The strength of the breed is explained by the large heart and lungs.

Thoroughbreds are often crossed with horses of other breeds to add speed and refinement. Thoroughbreds are classified among the "hot-blooded" breeds, animals bred for agility and speed, generally considered spirited and bold.

Registration

Unlike most registered breeds today, a horse cannot be registered as a Thoroughbred (with the Jockey Club registry) unless it is conceived by "live cover;" that is, by the witnessed natural mating of a mare and a stallion. Artificial insemination, though legal and commonly utilized in other horse breeds, cannot be used with Thoroughbreds. Originally this was because blood typing and DNA testing had not yet developed to a degree adequate to verify parentage. Today the reasons may be more economic: a stallion has a limited number of mares who can be serviced by live cover. Thus, the practice prevents an oversupply of Thoroughbreds to some extent. (Though modern management still allows a stallion to live cover more mares in a season than once was thought possible.) By allowing a stallion to only cover a couple hundred mares a year rather than the couple thousand possible with artificial insemination, it also preserves the high prices paid for horses of the finest or most popular lineages.