The law of the land in Thoroughbred breeding is simple: Cross a Thoroughbred with a Thoroughbred on a live cover, or find another registry. The rules in Quarter Horse racing allow for more creativity by breeders, which has drawn some of the Thoroughbred breed’s most recognizable names into the bloodlines of Quarter Horses. Thoroughbreds’ influence on the Quarter Horse breed trace back to Janus, a grandson of the foundation sire Godolphin Arabian who was imported to Colonial America in 1752 and crossed with the blood of Spanish Barbs—horses bred by the Chickasaw Indian tribe that were originally brought over by Spanish explorers—to lay the groundwork for the American Quarter Horse. In modern times, the impact of Thoroughbred sires such as Three Bars, Top Deck, and Beduino is still felt in today’s running Quarter Horse pedigrees, while the recent past has produced Grade 1 winners by Hennessy and 1997 Horse of the Year Favorite Trick. Even elite stallions such as Storm Cat and Alydar sired Quarter Horse runners. The American Quarter Horse Association’s Hall of Fame further displays the long-term relationship between the breeds, with seven Thoroughbred inductees. Another 18 Hall of Famers came from Thoroughbred sires or dams. As advances in artificial insemination have narrowed the gene pool in Quarter Horse breeding toward a handful of proven sire lines, Thoroughbreds have become a less popular option, but they still hold a niche in the market for their outcross potential and their ability to add stamina to a foal’s pedigree. “Nowadays, it seems like nobody wants to stick their neck out and do it,” said Fred Alexander of A & A Ranch in Anthony, N.M. “I remember back in the ’60s and ’70s, people would experiment with Thoroughbreds. They just don’t seem to do it anymore.” Appendix horses The AQHA has a special registry and numbering system for Quarter Horse-Thoroughbred crosses, referring to them as “Appendix” horses, with more than 600,000 registered to date. Appendix horses are eligible to compete in all AQHA competitions, including racing, without restriction, but they can only be bred back to a permanent, or regular-numbered, Quarter Horse. An Appendix horse cannot be bred to a Thoroughbred or another Appendix horse and still be registered with the AQHA. However, if an Appendix horse proves itself by earning a speed index of 80 or higher on the racetrack or by earning a Register of Merit in the open division of an AQHA-approved show, that horse can become eligible for advancement, loosening breeding restrictions on itself and its foals. Stallion qualities When considering a Thoroughbred stallion, Quarter Horse breeders often look for the same qualities they would seek from horses of their own breed. “The main thing breeders look at is the sprinting ability of those horses,” said Andrew Gardiner, general manager of JEH Stallion Station, which stands horses of both breeds in Oklahoma and Texas. “They’re not so much interested in the stamina as they are the sprinting ability of those Thoroughbreds.” Another important factor identified by Gardiner is the stallion’s look. He described the late Favorite Trick, a successful crossover sire at JEH, as having a heavy hip in terms of muscling, with a good amount of bone. His Quarter Horse-friendly build, paired with his award-winning sprinting ability, helped Favorite Trick sire a pair of AQHA champions. The most visible recent example of a successful crossover horse was a son of Favorite Trick, Good Reason SA, who was a multiple Grade 1 winner of $1,446,727 and earned the AQHA’s champion aged horse honors in 2011. Under normal circumstances, Good Reason SA would have been an ideal representative from the final crop of his sire, who died in a 2006 barn fire shortly after Good Reason SA was conceived. However, because Quarter Horse breeding allows artificial insemination with frozen semen, Favorite Trick remains available for breeding despite his once-insurmountable setback. Through intracytoplasmic sperm injection (ICSI), breeders are able to isolate a single sperm cell and inject it into an egg withdrawn from a mare. This process can potentially increase a stallion’s ability several hundredfold and keep his breeding career going long after death. Gardiner said that Favorite Trick’s supply could be available for another five to ten years. “With Feature Mr. Jess [a prominent Quarter Horse sire who died in 2009], we took one frozen semen straw, which at best would be one-quarter of an insemination, because at the very least you’d breed a mare with four straws,” Gardiner said. “In essence, you had a quarter-dose, and we had that straw changed into ICSI doses…We got back 400 ICSI straws.” The biggest drawback to ICSI breeding is the added expense associated with the process, potentially tacking on an additional $6,000 to $7,000 to the cost of breeding. Gardiner also said that many breeders simply move on after a stallion dies, even if he is still available for service. “Once a horse is gone, barring your top individuals in the breed, they simply aren’t sought after as much once they’re dead, regardless of how good they are when they go out,” he said. “You’re only talking about the top one or two percent which have enough draw to keep people interested enough to do something like that.” Familiar names Every so often, horseplayers may notice a Quarter Horse by a sire based at a major Kentucky farm. Often, these matings are the result of the stallion’s owner using his or her breeding rights to bend the rules, and the farm does not openly offer Quarter Horse breeding. One of the most notable exceptions to that was Storm Cat, who was briefly advertised for Quarter Horse services the year after he was pensioned from live cover stud duty in 2008 at Overbrook Farm in Lexington, Ky. With the help of a special fertility procedure developed at Texas A&M University, Storm Cat posted a stud fee of $20,000 for artificial insemination, a king’s ransom in the Quarter Horse world, but a far cry from the $300,000 he commanded during his final year at stud. Storm Cat sired only one Quarter Horse, a colt named Stray Cat out of champion Your First Moon. Bred by Vessels Stallion Farm and country music artist Lyle Lovett, Stray Cat has won one of 13 starts over three seasons of racing, most recently finishing second in a March 8 trials race at Sunland Park. The experiment, while short lived, made sense. Storm Cat’s reputation as a sire of sires carried over into the Quarter Horse realm, with no less than ten sons currently advertised for Quarter Horse services, along with many more from his sire line. Arguably the most successful of those sons has been the late Hennessy, who sired Grade 1 winners from both breeds. Racing Hall of Famer Alydar also briefly dabbled with Quarter Horse breeding, siring four foals, with one winner from two to race.