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Thoroughbred “speed gene” determines why some racehorses are sprinters and some stayers

Racehorses - Labelled for reuse


By Equestrian Life

Irish researchers have analysed race records and genetics of 3,000 racehorses from around the globe, and have found unequivocal evidence that a “speed gene” is the main determinant as to whether horses are born sprinters or stayers.

The study (The contribution of myostatin (MSTN) and additional modifying genetic loci to race distance aptitude in Thoroughbred horses racing in different geographic regions, E. W. Hill et al. Equine Veterinary Journal, January 2019) found that the myostatin gene is the almost singular genetic determinant of a horse’s optimum race distance. The research confirms a previous smaller-scale study conducted by the team, led by associate professor of equine science Emmeline Hill, which is based at the University College Dublin. The researchers believe their latest findings end any dispute over the central role of the speed gene as they were able to replicate and validate their original research on a much larger scale.

The conclusion of the study states:

“MSTN (myostatin gene) is the single most important genetic contributor to best race distance in the Thoroughbred. Employment of genetic prediction models will lead to more accurate placing of horses in races that are best suited to their inherited genetic potential for distance aptitude.”

The knowledge is very valuable to the thoroughbred industry, and while the initial research and subsequent genetic test wasn’t popular with science-adverse breeders, those newer to the industry have been more open to making use of it. The latest findings and confirmation of the importance of the speed gene may mean more breeders are likely to be open to utilising the genetic test. It also means that if you know the genetic profile of your horse, you can train it in such a way and place it in races that best suit its genetic potential.

The association between speed gene and distance is thought to be as statistically strong as the most genetic traits in humans – such as eye colour and the probability of going bald. The study found that in European horses, more than 83% of speed gene type known as “C:C” (sprint) horses had an optimum race distance of a mile or shorter, and more than 89% of “T:T” (staying) horses ran best over distances greater than a mile.

The main differences between sprinters and staying-type horses has been shown to be caused by a mutation in the speed gene that alters the rate of muscle growth and fibre-type differences in muscle. Although myostatin is the most important gene, the research identifies other genes which have moderate effects on the staying ability of a horse related to muscular response to exercise, regulation of fat metabolism and oxygen consumption.

Researchers believe that one concern with these findings is that people could be inclined to breed for sprinters (as this is where much of the big money is around the globe), ultimately putting the stayer at risk of extinction.

Will breeders continue to breed based on look and lineage, or is genetic testing for speed set to become the norm? We’ll have to wait and see.

Read the full study here.




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