The Modern Equine Vet
August 2023
Vol 13 Issue 8 2023
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News Notes

Genetics Driving Speed in Racehorses

By Duncan Sandes
University of Exeter

Improvements in genetics appear to be a factor for increasing speeds among Britain’s Thoroughbreds, which contradicts earlier studies. However, the new research also showed the rates of genetic progress are relatively low, particularly over long-distance races.

Researchers analyzed a data set of 692,534 race times run by more than 76,000 horses born between 1995-2012. Over sprint, middle-distance and long-distance races, genetic improvement for Thoroughbred speed was found to be ongoing and statistically significant.

The study found that genetic improvement accounts for 60%, 55% and 17% of the total increase in speed observed over short, middle and long distances, respectively.

The research also showed that Thoroughbred speed is only weakly heritable across all distances in part explaining the slow rates of genetic improvement.

The researchers suggest the low rates of genetic improvement also raise the possibility that selection of racehorses for breeding may be weaker than previously assumed, particularly over long distances, or some other constraint may be at play.

“There has been plenty of debate over the recent decades whether racehorses have reached a genetic limit to how fast they can run,” said Patrick Sharman, PhD, MSc, from the Centre for Ecology and Conservation at the University of Exeter’s Penryn Campus in Cornwall.

“Our analysis suggests that is not the case, and on the contrary, provides strong statistical evidence that racehorses continue to evolve to run faster in Great Britain. The question now is why are rates relatively low, particularly over long-distances?

“We estimated relatively low heritability for racehorse speed which goes some way to explaining it, but it would appear there is more to it. The selection of racehorses for breeding may be less accurate and weaker than generally assumed, particularly over long-distance races, but other factors could be constraining genetic improvement.” MeV

The article was originally posted here:
It was edited for style and length.


Patrick Sharman, Alastair J. Wilson. Genetic improvement of speed across distance categories in thoroughbred racehorses in Great Britain. Heredity, 2023; DOI: 10.1038/s41437-023-00623-8