Irish researchers catch up with the ‘speed gene’ in thoroughbred horses

Analysis of the race records and genetics of thousands of thoroughbred horses in leading racing countries of the world has provided unequivocal evidence that the so-called “speed gene” is the main determinant of why some horses are born sprinters, and others are born stayers.

The Irish research examined 3,000 thoroughbred racehorses which raced in Europe, Australia, South Africa and the US. It found the myostatin gene – the speed gene – is the almost singular genetic determinant of a horse's optimum race distance. This confirms earlier work on horses in Ireland and Britain conducted by the team based at University College Dublin.

The latest research, published this week in Equine Veterinary Journal, was led by UCD associate professor of equine science Emmeline Hill, who is also chief science officer at Irish equine science company Plusvital.

The notion of a single gene being responsible for a performance trait in thoroughbreds was previously challenged. However, Prof Hill said this study has ended any dispute over the central role of the speed gene. Her initial work involved a sample of hundreds of horses in Ireland and Britain.

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Multibillion

This knowledge is extremely valuable to thoroughbred breeders and trainers, in what is a multibillion euro industry. When the researchers made the initial breakthrough, it led to the development of a genetic test, but many in the industry were averse to science, preferring to concentrate on look and lineage. Newer breeders, however, embraced the test more readily.

“We have replicated and validated our original research findings on a massively larger scale. The power in the numbers has shown that the association of the speed gene with race distance is as statistically strong as the most highly genetically influenced traits in humans, including eye colour and the probability of an individual going bald,” she said.

In Europe more than 83 per cent of speed gene type known as “C:C” (sprint) horses had an optimum race distance of a mile or shorter, and more than 89 per cent of “T:T” (staying) horses ran best over distances greater than a mile.

The trend was consistent across major race regions globally, but the race pattern also influenced distribution of the speed gene types. In Australia, where there is an emphasis on early two-year-old speed, there were almost twice as many C:C horses among elite race winners in the population compared to Europe and North America (46 per cent compared to 26 per cent and 28 per cent, respectively) and there were almost seven times as many C:Cs as T:Ts within the Australian population.

Mutation

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.

This genetic information is leading to horses being trained and raced for their genetic potential

Prof Hill said the application of genetics to decision-making about how horses were trained and raced is transforming the industry. “Our results clearly show that using evidence-based science will lead to more accurate placing of horses in races that are best suited to their genetic potential. Horses are a product of their inherited genetic characteristics as well as the environment.

“The management of the horse is inarguably key in any horse’s success, but DNA differences are the undisputed differences that make them individuals. This genetic information is leading to horses being trained and raced for their genetic potential and is providing a clear economic advantage to owners and trainers,” she explained.

Relevance

The research has relevance for the wider thoroughbred population. “Since there is just one gene that is a major player in the sprinting versus staying stakes, it is extremely vulnerable to selection pressures.

“This has been recognised by the concern in the industry over the potential reduction in genetic diversity by favouring precocious, commercially-attractive horses. This concern is well justified – the staying type is at serious threat of extinction in the global population,” Prof Hill warned.

It was essential the industry incentivised breeding and racing of stayers to reduce the pressure to breed for the sales ring, she added.