Bloodhorse                                                                                                                                   April 3, 2006

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Geneticists identify speed gene combination  

By Mark Popham

Geneticists have disclosed the findings of a six-year study which, as well as discovering discrepancies in the stud book, for the first time details a direct correlation between specific genes and aspects of racing performance in Thoroughbreds.

Dr. Stephen Harrison of Thoroughbred Genetics Ltd, based in Kent, England, and Dr. Juan Luis Turrion-Gomez of the University of Salamanca, Spain, detected variations in eight athletically-important genes in DNA samples taken from 1,000 Thoroughbreds that raced as 3-year-olds in the UK in 2003, including classic winners.

The study, published in the peer-reviewed journal Mitochondrion, found that individual breeding lines possess variant combinations of these performance-related genes, with each combination giving a horse a different racing aptitude.

Harrison and his colleague, after observing the genetic types of the winners of 21 of the UK's premier races, found that horses carrying specific gene variants performed well over certain distances -- i.e., a winner of the Belmont Stakes (gr. I) at 12 furlongs is likely to be of a different genetic type to a Breeders' Cup Sprint (six furlongs) winner.

"We anticipate that the data could help trainers identify, from day one, optimum running distances for horses, develop appropriate training regimes, and help target specific races which will suit the horses' individual genetic profiles," Harrison said.

Intriguingly, the study found that the gene combinations are inherited solely from the dam, on a molecule known as mitochondrial DNA.

Harrison believes that his team's findings could remove much of the guesswork and risk involved in potential matings.

"Looking at it from a genetics point of view, you're better off trying to coordinate similar stamina components of genetics in one horse, instead of going for a mix and match approach and testing it on the racecourse," Harrison said.

Harrison believes that his genetic matching could be crucial to reinvigorating former stakes-winning families that have fallen into decline, while also proving that a mating between a sprinter and a stayer is likely to produce nothing more than a slow horse.

Harrison noted: "Breeding racehorses is a high-risk, multi-million dollar industry in which a high percentage of racehorse breeders fail to recoup their investments. The odds have for too long been stacked against the breeder, so use of advanced genetics techniques to modernize traditionally-based breeding programs can now narrow down the quest to produce a truly brilliant horse.

"These findings are only the tip of the iceberg," he continued. "They form part of a larger study which has allowed Thoroughbred Genetics to develop genetic databases covering national racing in the USA and Australia, which vary in their racing requirements from Europe."

The researchers also exposed historical errors in the stud book, some of which could be as recent as the 1970s, by looking at the mitochondrial DNA types of all big-race winners in the major racing nations going back as far as 100 years.

He reported: "The first part of the research looked at the stud book, comparing the results of DNA samples taken from 1,000 Thoroughbreds, to see how correct it was. You would expect that these genes, only inherited down the female line, should be the same for all horses descended down that line, but the fact was that they were not. Of the 33 different family lines we looked at, 19 had incorrect information. If you extrapolate that to all pedigrees, you could probably say that all pedigrees in existence are wrong to some degree."