Do Genetics Affect Racing Performance?

We know some Thoroughbreds are faster than others. But why? Some are back at the knee. Some are sounder than others. Some are more susceptible to infectious diseases than others. But why?

These, and countless other questions, were discussed during a four-day conference March 8-11 held at the Banbury Center of Cold Spring Harbor Laboratory on Long Island. The workshop, titled "Horse Genomics and the Genetics of Factors Affecting Horse Performance," received funding from the Dorothy Russell Havemeyer Foundation and Stonerside Stable owner Robert McNair.

Questions involving genetics and the relationship to horse diseases and performance will only be answered over time, even if the resources to decode the horse genome (locating and interpreting the function of all the genes) are available. But, scientists are in agreement that mapping the horse genome is extremely important, both to identify and treat equine diseases, and to breed sounder, healthier horses. It is more far fetched to think genomics will lead to breeding "super" horses.

The first International Equine Gene Mapping workshop was held in Lexington in 1995. Since that time, geneticists at various labs throughout the world have been busy mapping the horse in a friendly competition, led by Dr. Ernie Bailey of the Gluck Equine Research Center in Lexington.

Others who made presentations at the conference included Dr. Matthew Binns of the Animal Health Trust in Newmarket, England; Dr. Patrick Cunningham of Trinity College in Dublin, Ireland; Dr. Ann Bowling of the University of California at Davis; Drs. Jim Mickelson and Stephanie Valberg of the University of Minnesota; Dr. Jim Rooney of Queenstown, Md.; and Dr. W. R. (Twink) Allen of the University of Cambridge, England.

Also, several scientists studying and/or mapping other species were in attendance. Among them were human geneticist Dr. Aravinda Chakravarti of Case Western Reserve University; Dr. Mark Neff of the University of California at Berkeley, who specializes in dog genetics; and Dr. Stephen O'Brien of the National Cancer Institute, who is mapping cat genetics.

The scientists are working to identify genetic markers, the location of genetic information on chromosomes. Humans have 23 pairs of chromosomes while horses have 31 pairs.

Most of the available resources are being directed at the human genome. The globally conducted human genome project began in 1990 and scientists hope to have a "high resolution" map finished by 2005.

The first map of genes in the horse will be released this year, but it will contain far fewer "markers" than have already been identified in numerous other species.

Horse geneticists were told a 1,000 marker-map is a necessary minimum number for significant information. Achieving this number brings up an age-old dilemma for scientists: being able to study only what funding allows. To produce a map with 1,000 markers is estimated to cost up to $2 million.

Scientists at the meeting say decoding the horse's genes will prove highly beneficial to not only Thoroughbreds, but all breeds. With such a "high resolution" map, they say, it will be possible to begin work to study the heritability--the level at which a trait is believed attributed to genetics rather than environment--of such things as infectious diseases, soundness, wind problems, OCD, and lameness.

Because of the complex problem of defining racetrack performance--and how genetics could improve it--identifying the genetic link to health problems in Thoroughbreds will over time improve the breed as a whole, thus affecting performance indirectly.

The workshop was the suggestion of Charles E. Harris, who attended the entire conference. Harris is a horse owner and member of the President's Council of Cold Spring Harbor Laboratory.

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