Even as we celebrate this year's Triple Crown winner, it's time to take a hard look at what modern American breeding priorities may mean for the future of the Thoroughbred.
Only three years down the pike from American Pharoah, and we have another Triple Crown winner! Trainer Bob Baffert has expressed as much surprise as anyone else, but from my perspective the recent win by Justify was not a mere matter of luck. Baffert trained both Justify and American Pharoah, and there is no doubt in my mind that he possesses a superior concept of how to train and condition Thoroughbreds for classic distance racing.
In previous articles, we have examined several great racehorses of the past---Man o’ War, Phar Lap and Secretariat, comparing them in terms of pedigree, conformation and galloping style to the 2015 Triple Crown champion, American Pharoah (see “American Pharoah and the Triple Crown,” EQUUS 458). Secretariat, the 1973 Triple Crown winner, remains the absolute gold standard for speed in flat-track racehorses, with Man o’ War a close second (see “Secrets of Secretariat’s Speed,” EQUUS 434). This year’s win by Justify provides a fresh opportunity to look at trends in Thoroughbred breeding, variation in conformation and the galloping biomechanics of fast racehorses.
INBREEDING AND “PHALARIS CREEP”
I hope that anyone involved in Thoroughbred breeding will take note of the pedigree analyses presented in this article. Color-coded charts make trends stand out at a glance, and I’m not going to beat around the bush: By any biological measure, the future of the Thoroughbred is in jeopardy due to relentless inbreeding. This trend is evident across all disciplines, but it particularly afflicts flat-track racers.
As the increasing amount of red in the charts clearly shows, inbreeding is evident in every Triple Crown winner and contestant from about 1975 onward. All contestants in both the 2015 and 2018 Triple Crowns are sire-line descendants of a single horse, Phalaris, foaled in 1913, and all but one descend from this horse in damsire line as well. Worse, in the 2015 and 2018 fields, 52 percent and 46 percent respectively of all the horses who competed descend in either sire line or damsire line from Mr. Prospector, himself a double-Phalaris horse (Raise a Native x Gold Digger). All of the 2015 and 2018 contestants sired by Mr. Prospector came from Phalarisbred mares, creating foals intensely inbred to that one sire.
As early as 1966---before the modern era of DNA testing---researcher Ann T. Bowling utilized blood proteins to demonstrate that the Thoroughbred is the most inbred of all major horse breeds and warned of the deleterious effects of unchecked inbreeding. An important study reported in 2001 by E.P. Cunningham and colleagues at the University of Dublin estimated an inbreeding coefficient of 12.5 percent for the Thoroughbred population of about 300,000 individuals worldwide. By contrast, behavioral studies on free-ranging feral Camargue horses and American
mustangs have shown that after their first heat, young females normally disperse from their natal herd, seeking to join a group where they may be closely related to some females but distantly or not at all related to the males. This behavior naturally maintains a low degree of inbreeding. In parallel fashion, scientists managing the genetic health of captive endangered species, such as the Przewalski’s horse, seek to ensure that at least 90 percent of the genetic diversity in the species is maintained over a 100-year time period.
For this article, I analyzed the pedigrees not only for American Triple Crown contestants but also for graded stakes races of similar length in other countries, for the Melbourne Cup (two miles on turf), for Olympic-caliber
Grand Prix jumpers, for the British Grand National steeplechase (four miles, 514 yards on turf), and for the grueling Maryland Hunt Cup, which is not only four miles long but conducted on rolling terrain over solid fences up to five feet in height. Shockingly, I found “Phalaris creep” in all categories, with Grand Prix jumpers---whose athletic challenges are the most different from those of the flat-track racer---the least affected (to see more on this analysis, go to “Inbreeding Across The Board,” EquusMagazine.com).
Increasing creep is evident in all categories of flat-track racing. Why is this? Fundamentally, it is because modern racehorse breeders are not searching for rare alleles0 and are not seeking the kind of all elic diversity evident in
Justify captures the 2018 Preakness Stakes