Jersey Act

It had its roots in the desire of British horse breeders to halt the influx of American-bred racehorses of possibly impure bloodlines during the early 20th century.

Among the factors influencing its relaxation were the racing success of ineligible horses in Europe and the damage caused to British and Irish breeders by the unavailability of French Thoroughbreds during and after the Second World War.

[3] The outlawing of race-track betting in parts of the United States between 1900 and 1913 led to a large influx of American-bred horses into Britain and Ireland, giving rise to fears among British breeders that they would be swamped by the American bloodlines and their own stock would become worthless.

[1] The Jersey Act did have an immediate impact however, as the winner of the 1914 Epsom Derby, Durbar II, was ineligible for registration, as his dam, Armenia, was bred in the United States and was not herself eligible for the General Stud Book.

Lexington's pedigree on his dam's side was suspect in the eyes of British racing authorities, and, as he had been the leading sire of racehorses in the United States for 16 years, his descendants were numerous.

[4] The rule did adversely affect many British breeders as well, though, including even one senior member of the Jockey Club, Lord Coventry, whose successful line of racehorses was ineligible for registration.

[1] Initially there was little foreign complaint or organized opposition, probably owing to the effect of the gambling bans in the United States on the domestic horse market.

[18] Contributing to the lack of outcry was a legal ruling in New York allowing oral betting at racetracks, which led to the growth of racing in the United States; by 1920 the American breeding market had rebounded and was booming.

A number of American-bred horses carrying the lines of Lexington had already been imported into England, including Americus, Rhoda B, and Sibola, and because they were grandfathered in, they and their descendants were allowed to be registered in the General Stud Book.

[4] Horses that were ineligible for General Stud Book registration, but were allowed to race, were identified with a Maltese cross in programs and auction listings.

[29] The rule was subsequently modified in June 1949,[8] after the racing careers of a number of horses such as Tourbillon and Djebel persuaded the Jockey Club to reconsider.

In 1948 two of England's five classic races were won by half-bred horses, My Babu and Black Tarquin, prompting the Jockey Club to amend the rule in the preface to the General Stud Book,[4] to state that: Any animal claiming admission from now onwards must be able to prove satisfactorily some eight or nine crosses pure blood, to trace back for at least a century, and to show such performances of its immediate family on the Turf as to warrant the belief in the purity of its blood.

[25] Weatherby's further amended its regulations in 1969, introducing the word "thoroughbred" to describe the horses registered in previous volumes of the General Stud Book.