Shrewd Australian Thoroughbred breeders get the jump on their overseas counterparts

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Thoroughbred racing at Doomben Racecourse, in Brisbane, Queensland. Photo: Commander Keane (public domain) via Wikimedia Commons
Thoroughbred racing at Doomben Racecourse, in Brisbane, Queensland. Photo: Commander Keane (public domain) via Wikimedia Commons

An intriguing genetic signature has been identified in Australian Thoroughbreds, pointing to the success of generations of canny breeding aimed at success on the track.

Researchers in Ireland say that Australian Thoroughbreds have their own genetic identity.

Genes relating to behaviour, cardiac function, locomotion and skeletal muscle physiology are different in Australian Thoroughbreds, they report.

By selecting for favourable traits in these crucial areas, Australian breeders have made beneficial choices that have contributed to early two-year-old speed.

The genetic research, published this week in the open-access peer-reviewed journal PLOS ONE, was carried out by scientists at University College Dublin (UCD) and Irish equine science company Plusvital.

The work involved genetic analysis undertaken on blood taken from 99 Thoroughbreds, 49 of whom were Australian, with the other 50 from regions including Europe, North America and South Africa.

The study team identified specific chromosomal regions favourable to horseracing in Australia that have been used by breeders over generations to maximise success.

In their study, entitled “Selection in Australian Thoroughbred horses acts at a locus associated with early two-year speed”, the researchers found that genes relating to behaviour, cardiac function and locomotion have different patterns in Australian thoroughbreds compared to Thoroughbreds from elsewhere.

The research was led by UCD Professor in Equine Genomics Emmeline Hill, who is also chief science officer with Plusvital.

“There are more than 20,000 genes in the horse genome but some genes have particular versions that result in differences between horses,” she says.

“The optimal genetic ‘package’ for a horse is dependent on the environment in which it is required to perform.

“We have identified the set of genes that are most suited to horses racing in Australia.”

An emerging theme in Thoroughbred genomics research suggests a link between racecourse success and genes involved in behaviour.

“One of the most influential genes for racing in Australia mediates the actions of the stress hormone cortisol,” she explains.

“In Australia, the ability of a young horse to adapt to the rigours and stresses of early training may be particularly important, considering the emphasis on two-year-old racing.”

The researchers also found a link between the genes that have been most strongly selected by Australian breeders and faster speeds measured at the gallop during early two-year-old training. “This,” she said, “is evidence for the value Australian breeders place on genes contributing to juvenile speed.

“Australian thoroughbreds more commonly have a particular set of genes that in mice control the coordination of locomotion, a function that may be particularly relevant to sprint racing.

“There was also strong evidence for elite Australian horses to more commonly have these genes.

“The specifics of the optimal Australian genetic ‘package’ might explain why certain sire lines may be more or less compatible for success in Australia.

“There is now an opportunity to identify horses with the most suitable genetics for racing in Australia, which could be applied when considering shuttle stallions, or in the breeding and selection of racehorses.”

The researchers said their results indicate that there may be a differential selection for racing performance under racing and management conditions specific to certain geographic racing regions around the world.

Han H, McGivney BA, Farries G, Katz LM, MacHugh DE, Randhawa IAS, et al. (2020) Selection in Australian Thoroughbred horses acts on a locus associated with early two-year-old speed. PLoS ONE 15(2): e0227212. https://doi.org/10.1371/journal.pone.0227212

The study, published under a Creative Commons License, can be read here

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