Calvin Borel rode Super Saver to win the 2010 Kentucky Derby. Image: Churchill Downs When the Kentucky Derby winner crosses the finish line in front of 160,000 roaring spectators on May 5, there's a good chance it will have two copies of a gene that makes a horse a sprinter. The so-called speed gene, which several laboratories say determines whether a horse prefers a short sprint, a marathon or something in between, is just one of the genetic markers identified in the search for the roots of elite performance in thoroughbreds. Now the race is on among five or six commercial laboratories to convince thoroughbred breeders and buyers that testing for this gene and other markers is the road to the Triple Crown. In the meantime, the geneticists behind these companies scramble to lay claim to the best markers for athletic traits. Major thoroughbred farms are signing up horses for testing, even though some say they're not sure what the results mean. "We don't know what to make of it," says Elliott Walden, president, CEO and racing manager of Winstar Farms in Versailles, Ky. Winstar, the 685-hectare birthplace of 2010 Kentucky Derby winner Super Saver, is dabbling in genetic testing. "We don't know how to evaluate the information. We're still figuring it out." He's not the only one puzzling over these tests, which start at around $500 per horse. A presumed genetic advantage Equix Biomechanics is a company driven by data. The Lexington, Ky., concern advises on thoroughbred buying and breeding after gathering a mountain of data including 36 separate measurements of bone and muscle groups and a computer analysis of the horse's gait. Operated by Equix president, J. Todd Stewart, who in his past life performed statistical arbitrage for hedge funds, and owned by another numbers guy, Gary Knapp, who also came from a career in finance, the firm feeds its many measurements into a mathematical model that spits out, theoretically, the perfect horse—one that moves quickly, efficiently and—for those with Triple Crown aspirations—with enough endurance to win the longest of the three races, the 2.4-kilometer Belmont Stakes. Big Brown, winner of the 2008 Kentucky Derby and Preakness Stakes, was bred by the numbers in this formula on Knapp's Monticule Farm in Lexington. Now, the company is adding gene profiles to its analysis. Knapp recently had some of his own horses profiled. "I wasn't sure of the actual relevance," he says. "There are just so many variables impinging on the relative success of a particular runner that it's difficult to take one particular variable and say, 'That's the key.'" Alongside this growing interest in the emerging genetic field are beloved traditions of an earlier century—the heavy reliance on pedigree to determine racing quality. Pedigree remains the major predictor of a horse's sale price, says geneticist Matthew Binns, of Midway, Ky.–based The Genetic Edge and former professor of genetics at the University of London's Royal Veterinary College. Unfortunately, it is a less capable predictor of performance. People view pedigree as a surrogate for genetics, Binns says, "but there's a very poor correlation between pedigree and DNA data." Convincing the thoroughbred industry of pedigree's limits will take a revolution. Buyers routinely look back to a horse's 32 great, great, great grandparents when deciding which animal to buy. Binns points out that, on average, a great, great, great grandparent can contribute only about 3 percent of its genes to any individual. But even data-loving Knapp is in the sway of pedigree, extending his own analyses back not just five generations, but to the 128 ancestors in generation seven. Pedigree versus genetic testing Trading the pedigree tradition for genetic testing could save thoroughbred buyers money, the gene profiling companies contend. Emmeline Hill, the discoverer of the "speed gene," leads the Equine Exercise Genomics Group at University College Dublin in Ireland. She is also chairman of the commercial horse genetics laboratory, Equinome, Ltd., which she co-founded. She says her research shows buyers consistently overpay for horses that perform poorly. She evaluated the sale prices of 200 yearlings and compared the outlays with the animals' on-track performance.