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Thoroughbred Overview

The Thoroughbred a widely recognized and popular breed; synonymous with horse racing. Thoroughbreds are "hot-blooded" and known for their agility, speed and spirit. Thoroughbreds are classified among the "hot-blooded" breeds, which are animals bred for agility and speed and are generally considered spirited and bold. The word "thoroughbred" is incorrectly used to refer to any breed of purebred horse. While the term probably came into general use because the English Thoroughbred's General Stud Book was one of the first breed registries created. Horse breeders consider it incorrect to refer to any horse or other animal as a "thoroughbred" except for horses belonging to the Thoroughbred breed. As stated Thoroughbreds were the first to initiate a breed registry or stud book which is an official list of animals within a specific breed whose parents are known.
Thoroughbreds Closed Registry vs. Open Registries: The Thoroughbred registry is arguably the most stringent of any within the horse universe. It is closed which means that only Thoroughbred’s can be registered. As opposed to an open book which selects individual horses based on the goals of that registry. In additionally Thoroughbreds are also required to have two purebred (Thoroughbred) parents and “live cover” in which the parents physically mate. The strict registry requirements of the Thoroughbred breed has contributed to a breed consistency which is unmatched, however many critics feel that the breeds gene pool is shrinking to the detriment of the breed. It is argued that in open registries’ the breed can be strengthened by careful selection of all breed stock to improve the specific traits of that breed. Details about registration policies to follow.
Thoroughbred Fact: Thoroughbreds that are born in the Northern Hemisphere technically become a year older on 1 January each year, those born in the Southern Hemisphere turn one year older on 1 August. These artificial dates have been set to enable the standardization of races and other competitions for horses in certain age groups.
Thoroughbred – Characteristics: The typical Thoroughbred ranges between 15.2 to 17.0 hh (hands high, one hand is 4 inches) (62 to 68 inches / 157 to 173 cm), averaging 16 hh (64 inches (163 cm)). They are most often bay, seal brown, chestnut, black, or gray. Less common colors, recognized in the United States include roan and palomino. White is very rare, but is also recognized color separate from gray. The face and lower legs may be marked with white, but white will generally not appear on the body. Coat patterns that have more than one color on the body, such as Pinto or Appaloosa, are not recognized by mainstream breed registries. Good quality Thoroughbreds have 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.
Thoroughbred – History: The Thoroughbred as it is known today was first developed in 17th century England. Mares native to England were bred (Crossbred) with imported Arabian stallions. All modern Thoroughbreds can trace their pedigrees to three stallions originally imported into England in the 1600s and 1700s, and to 74 foundation mares of English and Oriental (Arabian or Barb) blood. During the 1700s and 1800s, the Thoroughbred breed spread throughout the world; they were imported into North America starting in 1730 and into Australia, Europe, Japan and South America during the 1800s. Millions of Thoroughbreds exist worldwide today, with over 118,000 foals registered each year worldwide.
Thoroughbreds are used mainly for racing, but are also bred for other riding disciplines, such as show jumping, combined training, dressage, polo, and fox hunting. They are also commonly cross-bred with other breeds to create new breeds or to improve existing ones, and have been influential in the creation of many important breeds, such as the Quarter Horse, the Standardbred, the Anglo-Arabian, and various Warmblood breeds.
Thoroughbred – Foundation Stallions: All modern Thoroughbreds trace back to three stallions imported into England from the Middle East in the late 17th and early 18th centuries: the Byerley Turk (1680s), the Darley Arabian (1704), and the Godolphin Arabian (1729). Other stallions of oriental breeding were less influential, but still made noteworthy contributions to the breed. These included the Alcock Arabian, D'Arcy's White Turk, Leedes Arabian, and Curwen's Bay Barb. Another was the Brownlow Turk, who, among other attributes, is thought to be largely responsible for the gray coat color in Thoroughbreds. The addition of Arabian bloodlines to the native English mares ultimately led to the creation of the General Stud Book (GSB) in 1791 and the practice of official registration of horses. Each of the three major foundation sires was, coincidentally, the ancestor of a grandson or great-great-grandson who was the only male descendant to perpetuate each respective horse's male line: Matchem was the only descendant of his grandsire, the Godolphin Arabian, to maintain a male line to the present; the Byerly Turk's male line was preserved by Herod (or King Herod), a great-great-grandson; and the male line of the Darley Arabian owes its existence to great-great-grandson Eclipse, who was the dominant racehorse of his day and never defeated. One genetic study indicates that 95% of all male Thoroughbreds trace their direct male line (via the Y chromosome) to the Darley Arabian. However, in modern Thoroughbred pedigrees, most horses have more crosses to the Godolphin Arabian (13.8%) than to the Darley Arabian (6.5%) when all lines of descent (maternal and paternal) are considered. Further, as a percentage of contributions to current Thoroughbred bloodlines, Curwen's Bay Barb (4.2%) appears more often than the Byerly Turk (3.3%). The majority of modern Thoroughbreds alive today trace to a total of only 27 or 28 stallions from the 18th and 19th centuries.
Thoroughbred – Foundation Mares: The mares used as foundation breeding stock came from a variety of breeds, some of which, such as the Irish Hobby, had developed in northern Europe prior to the 13th century. Other mares were of oriental breeding, including Barb, Turk and other bloodlines. The 19th century researcher Bruce Lowe identified 50 mare "families" in the Thoroughbred breed, later augmented by other researchers to 74. However, it is likely that fewer genetically unique mare lines existed than Lowe identified. Recent studies of the DNA of Thoroughbred mares indicate that some of the mare lines thought to be genetically distinct may actually have had a common ancestor; in 19 mare lines studied, the haplotypes revealed that they traced to only 15 unique foundation mares, suggesting either a common ancestor for foundation mares thought to be unrelated or recording errors in the GSB.
Thoroughbred – Early Racing History: Flat racing (Track Racing – US) existed in England by at least 1174, when four mile races took place at Smithfield, in London. Racing continued at fairs and markets throughout the Middle Ages and into the reign of King James I of England. It was then that handicapping, a system of adding weight to attempt to equalize a horse's chances of winning as well as improved training procedures, began to be used. During the reigns of Charles II, Queen Anne of Great Britain, King William III, and King George I the foundation of the Thoroughbred was laid. Under James' grandson, Charles II, a keen racegoer and owner, and James' great-granddaughter Queen Anne, royal support was given to racing and the breeding of race horses. With royal support, horse racing became popular with the public, and by 1727, a newspaper devoted to racing, the Racing Calendar, was founded. Devoted exclusively to the sport, it recorded race results and advertised upcoming meets. By the end of the 18th century, the English Classic races had been established. These are the St. Leger Stakes, founded in 1776, the Epsom Oaks, founded in 1779, and the Epsom Derby in 1780. Later, the 2,000 Guineas Stakes and the 1,000 Guineas Stakes were founded in 1809 and 1814. The 1,000 Guineas and the Oaks are restricted to fillies, but the others are open to racehorses of either sex aged three years. The distances of these races, ranging from 1 mi (1.6 km) to 1.75 mi (2.82 km), led to a change in breeding practices, as breeders concentrated on producing horses that could race at a younger age than in the past and that had more speed. In the early 18th century, the emphasis had been on longer races, up to 4 mi, (6.4 km) that were run in multiple heats. The older style of race favored older horses, but with the change in distances, younger horses became preferred.
Thoroughbred – Recent Racing History: Selective breeding for speed and racing ability led to improvements in the size of horses and winning times by the middle of the 19th century. Bay Middleton, a winner of the Epsom Derby, stood over 16 hands high, a full hand higher than the Darley Arabian. Winning times had increased to such a degree that many felt further improvement by adding additional Arabian bloodlines was impossible. This was borne out in 1885, when a race was held between a Thoroughbred, Iambic, considered a mid-grade runner, and the best Arabian of the time, Asil. The race was over 3 mi (4,800 m), and although Iambic was handicapped by carrying 4.5 stone (29 kg) (63 lbs) more than Asil, he still managed to beat Asil by 20 length. An aspect of the modern British breeding establishment is that they breed not only for flat racing, but also for steeple chasing. Up until the end of the 19th century, Thoroughbreds were bred not only for racing but also as saddle horses.
Thoroughbred – Jersey Act: Soon after the start of the 20th century, fears that the English races would be overrun with American-bred Thoroughbreds because of the closing of US racetracks in the early 1910s, led to the Jersey Act of 1913. It prohibited the registration of any horse in the General Stud Book (GSB) if they could not show that every ancestor traced to the GSB. This excluded most American-bred horses, because the 100-year gap between the founding of the GSB and the American Stud Book meant that most American-bred horses possessed at least one or two crosses to horses not registered in the GSB. The act was not repealed until 1949, after which a horse was only required to show that all his ancestors to the ninth generation were registered in a recognized Stud Book. Many felt that the Jersey Act hampered the development of the British Thoroughbred by preventing breeders in the United Kingdom from using new bloodlines developed outside of the British Isles.
Thoroughbreds in America:The first Thoroughbred horse in the American Colonies was Bulle Rock, imported in 1730 by Samuel Gist of Hanover County, Virginia. Maryland and Virginia were the centers of Colonial Thoroughbred breeding, along with South Carolina and New York. During the American Revolution importations of horses from England practically stopped but were restarted after the signing of a peace treaty. Two important stallions were imported around the time of the Revolution; Messenger in 1788 and Diomed before that. Messenger left little impact on the American Thoroughbred, but is considered a foundation sire of the Standardbred breed. Diomed, who won the Derby Stakes in 1780, had a significant impact on American Thoroughbred breeding, mainly through his son Sir Archy. John F. Wall, a racing historian, said that Sir Archy was the "first outstanding stallion we can claim as native American." He was retired from the racetrack because of lack of opponents.

After the American Revolution, the center of Thoroughbred breeding and racing in the United States moved west. Kentucky and Tennessee became notable centers. Andrew Jackson, later President of the United States, was a breeder and racer of Thoroughbreds in Tennessee. Famous match races held in the early 19th century helped popularize horse racing in the United States. One took place in 1823, in Long Island, New York, between Sir Henry and American Eclipse. Another was a match race between Boston and Fashion in 1838 that featured bets of $20,000 from each side. The last major match races before the American Civil War was both between Lexington and Lecompte. The first was held in 1854 in New Orleans, Louisiana and was won by Lecompte. Lexington's owner then challenged Lecompte's owner to a rematch, held in 1855 in New Orleans and won by Lexington. Both of these horses were sons of Boston, a descendant of Sir Archy. Lexington went on to a career as a breeding stallion, and led the sires list of number of winners for sixteen years, fourteen of them in a row.
After the American Civil War, the emphasis in American racing changed from the older style of four-mile (6 km) races in which the horses ran in at least two heats. The new style of racing involved shorter races not runs in heats, over distances from five furlongs up to 1.5 miles (2.4 km). This development meant a change in breeding practices, as well as the age that horses were raced, with younger horses and sprinters coming to the fore. It was also after the Civil War that the American Thoroughbred returned to England to race. Iroquois became the first American-bred winner of the Epsom Derby in 1881. The success of American-bred Thoroughbreds in England led to the Jersey Act in 1913, which limited the importation of American Thoroughbreds into England. After World War I, the breeders in America continued to emphasize speed and early racing age but also imported horses from England, and this trend continued past World War II. After World War II, Thoroughbred breeding remained centered in Kentucky, but California, New York, and Florida also emerged as important racing and breeding centers.
Thoroughbred racehorses perform with maximum exertion, which has resulted in high rates of accidents and other health problems. Racing has been proven to have a higher fatality rate than all other legal human and animal sports. Also, Thoroughbreds are prone to other health complications, including bleeding from the lungs, low fertility, abnormally small hearts and a small hoof to body mass ratio. There are several theories for the reasons behind the prevalence of accidents and health problems in the Thoroughbred breed, and research continues into how to reduce the accident rate and treat those animals that are injured.

Thoroughbreds in the United States have historically been used not only for racing but also to improve other breeds. The early import, Messenger, was the foundation of the Standardbred, and Thoroughbred blood was also instrumental in the development of the American Quarter Horse. The foundation stallion of the Morgan breed is held by some to have been sired by a Thoroughbred. Between World War I and World War II, the U.S. Army used Thoroughbred stallions as part of their Remount Service, which was designed to improve the stock of cavalry mounts.
 In Europe
Thoroughbreds began to be imported to France in 1817 and 1818 with the importation of a number of stallions from England, but initially the sport of horse racing did not prosper in France. The first Jockey Club in France was not formed until 1833, and in 1834 the racing and regulation functions were split off to a new society, the Societe d'Encouragement pour l'Amelioration des Races de Chevaux en France, better known as the Jockey-Club de Paris. The French Stud Book was founded at the same time by the government. By 1876, French-bred Thoroughbreds were regularly winning races in England, and in that year a French breeder-owner earned the most money in England on the track. World War I almost destroyed French breeding because of war damage and lack of races. After the war, the premier French race, the Grand Prix, resumed and continues to this day. During World War II, French Thoroughbred breeding did not suffer as it had during the first World War, and thus was able to compete on an equal footing with other countries after the war.

Organized racing in Italy started in 1837, when race meets were established in Florence and Naples and a meet in Milan was founded in 1842. Modern flat racing came to Rome in 1868. Later importations, including the Derby Stakes winners Ellington (1856) and Melton (1885), came to Italy before the end of the 19th century. Modern Thoroughbred breeding in Italy is mostly associated with the breeding program of Federico Tesio, who started his breeding program in 1898. Tesio was the breeder of Nearco, one of the dominant sires of Thoroughbreds in the later part of the 20th century. Other countries in Europe have Thoroughbred breeding programs, including Germany, Russia, Poland, and Hungary. However, none of these countries have made a large mark on the breeding of Thoroughbreds.
Thoroughbreds in Australia and New Zealand: Horses arrived in Australia with the First Fleet in 1788 along with the earliest colonists. Although many horses of part-Thoroughbred blood were imported into Australia during the late 1700s, it is thought that the first pureblood Thoroughbred was a stallion named Northumberland who was imported from England in 1802 as a coach horse sire.[65] By 1810, the first formal race meets were organized in Sydney, and by 1825 the first mare of proven Thoroughbred bloodlines arrived to join the Thoroughbred stallions already there. In 1825, the Sydney Turf Club, the first true racing club in Australia, was formed. Throughout the 1830s, the Australian colonies began to import Thoroughbreds, almost exclusively for racing purposes, and to improve the local stock. Each colony formed its own racing clubs and held its own races.[65] Gradually, the individual clubs were integrated into one overarching organization, now known as the Australian Racing Board. Thoroughbreds from Australia were imported into New Zealand in the 1840s and 1850s, with the first direct importation from England occurring in 1862.
In other areas
Thoroughbreds have been exported to many other areas of the world since the breed was created. Oriental horses were imported into South Africa from the late 1600s in order to improve the local stock through crossbreeding. Horse racing was established there in the late 1700s and early 1800s, and Thoroughbreds were imported in increasing numbers. The first Thoroughbred stallions arrived in Argentina in 1853, but the first mares did not arrive until 1865. The Argentine Stud Book was first published in 1893. Thoroughbreds were imported into Japan from 1895, although it was not until after the World War II that Japan began a serious breeding and racing business involving Thoroughbreds.
Thoroughbred - Registration, Breeding, and Population: About 37,000 Thoroughbred foals are registered each year in North America, with the largest numbers being registered in the states of Kentucky, Florida and California. Britain produces about 5,000 foals a year, and worldwide, there are more than 195,000 active broodmares, or females being used for breeding, and 118,000 newly registered foals in 2006 alone. The Thoroughbred industry is a large agribusiness, generating around $34 billion in revenue annually in the United States and providing about 470,000 jobs through a network of farms, training centers and race tracks.

Unlike a significant number of registered breeds today, a horse cannot be registered as a Thoroughbred (with The Jockey Club registry) unless conceived by "live cover"; that is, by the witnessed natural mating of a mare and a stallion. Artificial insemination (AI) and embryo transfer (ET), though commonly used and allowable in many other horse breed registries, cannot be used with Thoroughbreds. One reason is that a greater possibility of error exists in assigning parentage with AI, and although DNA and blood testing eliminate many of those concerns, AI still requires more detailed record keeping. The main reason, however, may be economic: a stallion has a limited number of mares who can be serviced by live cover. Thus, the practice prevents an oversupply of Thoroughbreds, 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 cover only a couple hundred mares a year rather than the couple thousand possible with AI, it also preserves the high prices paid for horses of the finest or most popular lineages.

Concern exists that the closed stud book and tightly regulated population puts Thoroughbred bred at risk. With a closed stud book and the requirement of both parents being purebred Thoroughbred creates a lack of genetic diversity, with a level of unintended inbreeding inevitable with such a small genetic pool. According to one study, 78% of all Thoroughbreds in the current population can be traced to 30 foundation animals, 27 of which are male. Ten foundation mares account for 72% of maternal (tail-female) lineages, and, as noted above, one stallion appears in 95% of tail male lineages. Thoroughbred pedigrees are generally traced through the maternal line, called the "distaff" line (a direct mare line). The line that a horse comes from will often determine the price paid regardless of the actual talent or potential of the horse.

Contact: Thoroughbred Owners and Breeders Association -