There is a reason for that. Finding a specific gene responsible for racing performance "takes a lot of work and a lot of time," says Steven Tammariello, the lead geneticist for Lexington-based Performance Genetics. "Ultimately, it may not be that useful." It also costs a lot of money.
Instead, companies rely on genome-wide association studies, which scan for patterns and similarities. For instance, Tammariello looked at 65,127 single-nucleotide polymorphisms (SNP) in hundreds of horses, half of which were winners of elite races. In that search, he found 12 SNPs that associated with the best horses. These SNPs are the basis for any tests Performance Genetics conducts; it looks to see what alleles each tested horse possesses at these 12 locations. The more the horse has in common with a champion, the better it scores.
As for the "speed gene" Tammariello, also an associate professor of biology at Binghamton University in New York State, dismisses the prominence Hill accords it. "We found three other places that are also very important to distinguishing a sprinter from a route runner." And forget about it as an indicator for speed. "I owned two sprinters. I know they had the CC polymorphism, and they were terrible. It has nothing to do with the class of the horse," he says.
Dav Doodnauth, an MD and CEO of LifeLine Labs in Lexington, also uses genome-wide association studies to produce his "Pegasus Profiles." The internal medicine specialist says myostatin plays only a minor role in his analysis. "I don't think there is necessarily one area of the genome that's going to tell you everything about performance," Doodnauth says. Human athletic performance involves interactions of some 220 genes; the situation is likely to be the same in horses. "Myostatin markers are just a handful of the makers that we look at," he notes.
The Genetic Edge's Binns, who also published a research paper laying claim to the myostatin finding about a year after Hill did, says half of the 10 or so Kentucky Derby winners his company tested had two copies of the sprint version of the myostatin gene. One horse had two copies of the endurance version of the gene, and the rest had one copy of each. (He wouldn't say which winner had which combination.) His analysis: The "speed gene" isn't the sole determinant of Derby victory. "I think you get into difficult water if you base your breeding program on one gene," he says.
Nor will studying a horse's build and posture reveal what genes tell, Binns says. "You can't see these markers," he adds. "The best looker in the world cannot see these markers."
Other "silver bullets"
If the notion of a genome laid bare is enticing to some breeders and buyers, it's worrisome to those who have watched other technologies become the newest new thing.
"Everybody's looking for the silver bullet," says Kerry Cauthen, managing partner of the consignor Four Star Sales in Lexington—a job he says is somewhere between a matchmaker for horse buyers and sellers and the person who authenticates paintings at Sotheby's. He's seen such purported silver bullets before. Two examples: sometime in the 1990s, shoppers began demanding x-rays for any horse they considered buying. Whereas this was a useful tool in some cases, in others it led buyers to eliminate animals unnecessarily from consideration, Cauthen says. For instance, when an x-ray showed osteochondritis, or a split in the cartilage, in the hock—on a horse's hind leg, analogous to our ankle—buyers would lose interest, and good horses lost value. "It just tanked a sale. This horse is now worth a quarter or half of what he had been," Cauthen says. But osteochondritis is common in young animals, and often has no impact on a horse's training and performance, as later evidence showed.