Don't Fear the Speed Gene -- by Eric Mitchell

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Breeders interested in producing classic horses have long looked for the right genetic mix of speed and stamina. An article by Avalyn Hunter does a good job of examining the different breeding theories and their successes in the Feb. 13th issue of The Blood-Horse. As I read this piece, I could not help but think of the recent announcement by Irish genetics researcher Dr. Emmeline Hill that a “speed gene” for the Thoroughbred had been identified. Dr. Hill is the co-founder of a company called Equinome that provides a test for the gene, which affects the development of muscle mass. The Blood-Horse's Bloodstock Editor Dede Biles will have a more detailed explanation of the test and what it shows in the Feb. 20th issue, but in short the test reveals one of three gene types. C/C is found in a horse that is genetically suited to run (and hopefully win) between five and eight furlongs, C/T is the gene found in a horse suited to run between eight and 12 furlongs, and T/T is the gene found in horses suited to races at 10 furlongs and longer.

News of this genetic test have generated mixed reactions. Some see it as a terrible thing for Thoroughbred breeding, with the risk that people will eventually focus too much on the genetic results and less on other important factors such as conformation and pedigree. There has also been concern that genetics testing will replace time-testing breeding theories and the need for all those great statistics, such as average winning distance and dosage.

I see Dr. Hill’s test as something quite positive—another tool available to Thoroughbred breeders that helps them understand the genetic potential of their breeding stock. After all, what are all those statistics and indices the industry has labored to create over the years other than our best efforts to assess a horse’s genetic proclivity based on the information available? Going back to Hunter’s article, a popular breeding strategy is to breed sires with brilliant speed to mares with stamina. James Keene is often credited as the first American breeder to apply this theory. He bred winners of the Epsom Oaks, Jockey Club Stakes (1 1/2 miles at Newmarket, England), and the Belmont Stakes. Now with genetic testing, you’ll have another tool to know if a sire’s or mare’s genetic potential leans toward speed or stamina. Wouldn’t this be helpful for a broodmare prospect out of a stakes-producing family that never made it to the races because of injury?

The speed gene is no silver bullet. Dr. Hill admits this in an informative video posted on the Equinome Web site.

“We have developed the test to show what a horse is likely to be good at, not how good it’s likely to be,” she said.

No guarantees you’ll get a stakes winner or even a winner. You just know, based on the make-up of its muscle physiology, that the horse is likely to prefer short, intermediate, or long distances. Thoroughbred breeding is a game of percentages, and skilled breeders find ways to move the percentages in their favor.

Could a C/C horse ever win a race over a mile? Never say never. But the research apparently shows it is very unlikely. Genes are complicated things. They are affected by other genes in an individual’s genome and triggered by environmental influences. And I think every breeder and owner knows, or should know, that the most physically gifted horse can be compromised by inadequate nutrition or ruined in the hands of a bad trainer.

The genetic genie was let out of the bottle a long time ago. We will face ethical questions we never dreamed of and will see research to genuinely fear. But this breakthrough isn’t among them.— Eric Mitchell

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