A Thoroughbred is a horse whose parentage traces back to any of the three 'Founding Sires' the Darley Arabian, Byerly Turk and Godolphin Barb, and who has satisfied the rules and requirements of The Jockey Club and is registered in 'The American Stud Book' or in a foreign stud book recognised by The Jockey Club and the International Stud Book Committee. Any other horse, no matter what its parentage, is not considered a Thoroughbred for racing and/or breeding purposes.