What to Know About the Thoroughbred Horse

Medically Reviewed by Vanesa Farmer, DVM on January 20, 2023
Written by Sarah Vallie
5 min read

Perhaps the most well-known horse race in the U.S. is the Kentucky Derby. This race happens at the end of a two-week festival every May and is just for three-year-old Thoroughbred horses. Thoroughbreds are bred for strength and speed, making them the perfect racehorses. This breed has a long and accomplished history. Keep reading below to learn more Thoroughbred horse information.

Thoroughbred horses are a breed of horse that trace their origins back to three key sires, or “father” horses: Darley Arabian, Godolphin Arabian, and Byerly Turk. The owners, for whom the horses are named, transported the horses to England from the Middle East in the late 17th and early 18th century. Once in England, these horses bred with the stronger native horses to produce stronger, faster offspring. Since then, breeders have bred Thoroughbreds for strength, speed, and stamina. 

Bulle Rock, son of Darley Arabian, was the first Thoroughbred in America. Brought to Virginia in 1730, he had already been a successful racehorse for many years in Britain. By the year 1800, more than 300 Thoroughbreds had followed him to America.  

Thoroughbred horse racing. Horse racing has been a sport for centuries. The first written record of horse racing that has been found dates back to 664 B.C.E. from the Olympics. Evidence finds that other ancient cultures, like the Egyptians and Romans, practiced some form of horse racing as well. These cultures, especially the land-conquering Romans, spread horse racing across the globe.

The Romans brought horse racing to England, and the sport stayed after they left. Horse racing varied in popularity over the years and was even banned at one point, before Charles II brought it back with a vengeance in 1660. It was during his range that the three Thoroughbred sires reached England’s shores, and many of their offspring became star racehorses.

In the U.S., horses had been racing since 1665, but official Thoroughbred racing didn’t begin until Maryland governor Samuel Ogle put on the first Thoroughbred race in 1745. Thoroughbred racing has flourished in the U.S. since then, with iconic events like the Kentucky Derby showcasing the best Thoroughbred racehorses every year.  

Thoroughbred horse registries. To ensure effective selective breeding, it’s important to keep reliable records. When the breeding of Thoroughbreds first began, these records weren’t well-kept. In 1791, James Weatherby published the first volume of the General Stud Book, which listed the ancestry record, or pedigree, of 387 mares (adult female horses). Each of these horses had a lineage that could be traced back to Eclipse, the son of Darley Arabian; Matchem, the grandson of Godolphin Arabian; or Herod, the great-great-grandson of Byerly Turk. The General Stud Book continues to be published in England to this day.

The American Stud Book followed in 1873. Colonel Sanders D. Bruce, who had spent most of his life researching the lineage of American Thoroughbreds, stayed true to the format of the original when he published the first volume. By 1896, there were six volumes of the American Stud Book, at which time the publication was taken over by the Jockey Club. 

The Jockey Club, established in 1894, still oversees the American Stud Book, which registers documented Thoroughbreds in the U.S., Canada, and Puerto Rico. Since 2001, they’ve used DNA testing to establish the integrity of a Thoroughbred’s bloodline.

Thoroughbreds are an elegant, athletic breed of horse. They have chiseled heads with wide eyes and long necks. Because they’re bred for speed, thoroughbreds often have lean bodies, long legs, and muscular shoulders. They’re typically seen with a curved back and wide hips. Typically, Thoroughbred size is 15 to 17 hands (60 to 68 inches) tall and 990 to 1,200 pounds (450 to 550 kilograms).

The coats of Thoroughbred horses come in multiple colors. Currently, the Jockey Club recognizes the following colors for Thoroughbreds:

  • Bay: A bay horse is primarily brown, which may range from yellow-tan to auburn, with black manes, tails, and lower legs.
  • Black: In a black horse, the entire horse, including the mane and tail, is black.
  • Brown: Horses that are considered brown include horses with brown coats and tan on the flanks (belly), head, and shoulders, or horses with dark brown coats with tan on the flanks and muzzle (area of the head with the mouth, chin, and nostrils). Brown horses have black manes, tails, and lower legs.
  • Chestnut. Chestnut horses can vary from reddish-yellow to golden yellow. The mane, tail, and legs are usually a similar color.
  • Gray: Gray horses have a coat with a mix of black and white hairs, creating a gray tone. Their mane, tails, and legs are either black or gray.
  • Palomino: Palomino horses are golden with flaxen (the color of hay) manes and tails. 
  • Roan: Roan horses have coats that are a mix of either red and white hairs or brown and white hairs. Their manes, tails, and legs can be black, chestnut, or roan.
  • White: White horses have coats, legs, manes, and tails that are predominantly white. 

While Thoroughbred horses may come with a coat that has more than one color, these horses are not recognized by breed registries like The Stud Book. However, white markings on the face and body are acceptable.

Thoroughbred horses are known for their excellent temperament. They’re smart and full of energy, and they often have a strong work ethic. The Thoroughbred personality is usually very spirited. As a result, they may be better suited for experienced riders, as they may be too bold for beginners. This temperament makes them excellent horses not only for racing but for other equestrian sports like dressage and jumping. They’re also excellent for hunting.

Retired racehorses may be easily spooked from their time on the track and need some extra care and training for general riding. Several charities work to rehome ex-racehorses and give them a new life after racing.

The average life expectancy of a Thoroughbred horse is 25 to 35 years.

Due to inbreeding, some Thoroughbreds may be more prone to health issues such as:

  • Abnormally small hearts
  • Bleeding from the lungs
  • Lameness due to an unbalanced hoof-to-body size ratio
  • Low fertility

Thoroughbred racehorses may experience injuries from racing, including accidents on the racetrack, stress fractures, and bone chips. 

Thoroughbred horses eat a diet mainly made up of fiber. While the specific diet will depend on the horse's age, breed, and weight, most horses primarily eat grass, hay, or a hay replacement. Horses are grazers, so they eat small amounts often throughout their day.

  • The fastest racehorse was a Thoroughbred named Winning Brew, who ran at a speed of 43.97 miles per hour over two furlongs (a quarter of a mile).
  • The United States is the world’s largest producer of Thoroughbred horses.
  • Thoroughbreds have been cross-bred to help create other breeds like the American Quarter Horse and the Anglo-Arabian breed.
  • In 1907 and 1908, a Thoroughbred named Colin was unbeaten, winning all 15 of his starts, including the Belmont Stakes.
  • Thoroughbred racing brings in $500 million in government revenue every year.