Kentucky Derby Challenge Stakes Kentucky Derby Challenge Stakes The Kentucky Derby Challenge Stakes was an English Thoroughbred horse race intended to become an annual race, but was run only one time on 18 March 2009 at Kempton Park Racecourse in Sunbury-on-Thames, Surrey. Open to three-year-old European horses, it was raced clockwise at a distance of nine furlongs ( miles, app. 1800 metres) on Polytrack. The winner of the race was guaranteed one of the twenty starting spots in the mile (10 furlongs) 2009 Kentucky Derby held on the first Saturday in May on the dirt track at Churchill Downs in Louisville, Kentucky. The race
American Quarter Horse hence the nickname. Horses listed in the appendix may be entered in competition, but offspring are not initially eligible for full AQHA registration. If the Appendix horse meets certain conformational criteria and is shown or raced successfully in sanctioned AQHA events, the horse can earn its way from the appendix into the permanent studbook, making its offspring eligible for AQHA registration. Since Quarter Horse/Thoroughbred crosses continue to enter the official registry of the American Quarter Horse breed, this creates a continual gene flow from the Thoroughbred breed into the American Quarter Horse breed, which has altered many of the characteristics