Do Studs Make Winners?

Trevor Butterworth

One of the most enjoyable studies to come out over the holiday period struck a blow against the genes are destiny theory of life – at least on the racetrack. After analyzing the race results and lifetime prize winnings of 554 stallions and their ancestors to 4 generations, Alastair Wilson and Andrew Rambaut, two evolutionary biologists at the University of Edinburgh, concluded that the vast sums of money spent on stud fees have little impact on future purses.

In a study published in Biology Letters, a mostly online, peer-reviewed journal of Britain’s Royal Society, the researchers note that genetic tools are increasingly being used to breed race horses given that “quantitative and molecular approaches have revealed genetic variation for key racing performance traits.” In other words, there appears to be good scientific grounds for the commonsense wisdom that mating a thoroughbred mare with a successful stallion is the best way to produce winners on the track.

But does this justify paying exorbitant stud fees – up to $50 million a year, according to the Guardian newspaper – on horses with prize-winning reputations? Are stud fees actually reflective of genetic quality and potential?

Given that mating is determined by human intervention and not the natural interplay of horses, it turns out that the monetary values attributed to stallions for reproduction are not indicators of future winners. Wilson and Rambaut’s pedigreed database of 4,476 horses foaled between 1922 and 2003 revealed that, while lifetime earning is heritable, the stud fees do not correlate with winning potential. Instead, over 90 percent of the genetic variance among top prize winners is attributable to other factors, such as how the horse is trained, cared for, and ridden.