The Thoroughbred is a breed of horse that was developed in England during the reigns of King Charles II, King William III, Queen Anne, and King George I. The foundation stallions of the breed, two Arabians and one unknown breed, were imported in the late seventeenth and early eighteenth centuries, and although nearly 160 Oriental stallions were used in its development, these three horses were the most prominent. These were bred to native mares from various breed, including the Irish Hobby, and by 1791 the crossing of these breeds had become so successful that the General Stud Book was established, developing a system for organized registration.

Racing has been popular in England since 1174, but the Thoroughbred had not been changed to fit these races until the early eighteenth century, when races became shorter. Breeders began focusing on the speed of their horses rather than the endurance and by the nineteenth century, the Thoroughbred was larger and more capable of winning races. Thoroughbred horses were first brought to America in 1730 and they became popular race horses in many areas. Breeding practices changed after the American Civil War, when racing styles changed from long races to shorter races.

When American horses began winning races in England, a new law known as the Jersey Act was passed in 1913, which prevented most horses from registering in the GSB, thereby preventing them from racing. Around the same time World War II ended, this law was repealed and Thoroughbreds were imported and exported from both countries in order to improve bloodlines. Today, closed studbooks and strict breeding requirements have caused some concern about genetic diversity, although there are over 195,000 breeding mares in the world and thousands of foals are registered each year.

The Thoroughbred can reach a height between 15.2 and 17 hands, although 16 hands is the most common height. It has a well-defined head, long neck, short back, and long legs, with a generally slender body conformation. This breed is typically bay, black, brown, chestnut, or gray in color, but some individuals can be roan or palomino in the United States. It is known for its spirited temperament as well as its speed and agility.

The Thoroughbred has been bred throughout its history for racing purposes, but it can also be used for other events such as show jumping and dressage, among many other Western and English sports. It has also been used in the development and improvement of many breeds including the American quarter horse and the Anglo-Arabian. Because this breed is bred primarily for racing, it can succumb to a number of illnesses and injuries including orthopedic issues, exercise induced pulmonary hemorrhage, and general lameness due to small hooves. It suggested that these cause of these ailments might be inbreeding or poor breeding, or excess stress which creates a higher risk for accidents.

Image Caption: Thoroughbred race horse. Credit: Goki/Wikipedia (CC BY-SA 3.0)