The price of good genes: Unlike the quality of a peacock's tail, new research shows that the stud fee of stallions is not a reliable indicator of their genetic quality.

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SYDNEY: A new genetic analysis of racehorses shows that, as far as the stud fees of stallions go, you don't necessarily get what you pay for.

A survey of the genealogy and success of 4,000 racehorses reveals that, though genes accounted for 10 per cent of the variation in the lifetime earnings of these horses, that isn't reflected in the vast stud fees breeders sometimes pay for the 'best' stallions.

Horse racing is a multi-billion dollar industry and breeders are prepared to pay huge sums to buy an opportunity for their mares to be mated by the most highly reputed stallions.

Multi-billion dollar industry

"While there are good genes out there to be bought, the best genes don't necessarily come with the highest price tag," said lead researcher Alastair Wilson, of the University of Edinburgh's Institute of Evolutionary Biology in Scotland.

To probe the relationship between expense and success, Wilson and co-worker Andrew Rambaut compared the stud fees, winnings and lifetime earnings of more than 4,000 horses used for breeding and racing in the U.K. and U.S. since 1922. They also studied the family trees of these horses.

They found that inheritance accounted for about 10 per cent of the variation in the amount of earnings a horse would make in prize money throughout its career – but that environmental factors, such as better management, trainers and jockeys, accounted for 90 per cent of the lifetime earnings.

But, as they report today in the British journal Biology Letters, when the researchers further studied the relationship between this genetic component of success and the stud fees paid for stallions, they found no link.

Nurture more than nature

"The offspring of expensive stallions might tend to win more money, but not necessarily because they have inherited the best genes," said Wilson. "It is likely that those breeders best able to pay high stud fees are also those who are able to spend more on care of the horse, how it is trained, and who rides it - all of which will contribute more to how much it will win."

The researchers argue there could be a silver lining to the find in that breeders could get much better value for money by testing horses for good genes, rather than just selecting the most expensive stallions.

Over recent years studies have revealed genetic variation in number of key traits for racing performance – such as stamina, which has been linked to mitochondrial genes passed down the maternal line.