A study published Thursday in the Equine Veterinary Journal determined the myostatin gene, or "Speed Gene," is the main genetic determinant of a racehorse’s optimum distance. And, according to the lead researcher, pressure from the commercial market could effectively do away with stayers, or distance horses, for more precocious and sprint-type runners.
The research was led by Emmeline Hill, an Equine Science associate professor at University College Dublin and the chief science officer of Plusvital, an Irish equine science company. Genetics and race records of more than 3,000 Thoroughbreds from Europe, Australia, South Africa and the United States were analyzed. In Europe, more than 83 percent of racehorses with the ‘Speed Gene’ (type C:C) had optimum distances of a mile or less, and more than 89 percent of racehorses with type T:T had an optimum distance beyond a mile.
Hill said the study puts to rest any challenges of myostatin playing the most important role in determining a racehorse’s distance ability.
“We have replicated and validated our original research findings on a massively larger scale," she said. "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 color and the probability of an individual going bald."
The study found the trend consistent across all the analyzed regions, with the types of races influencing the ‘Speed Gene’ distribution. Australia is known for its speedy juveniles, and 46 percent of their racehorses were found to be type C:C. In North America only 28 percent had the ‘Speed Gene,’ and 26 percent of the European racehorses analyzed were found to be C:C.
The study also revealed within Australia alone, there were nearly seven times the amount of C:C horses as there were T:T horses.
“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,” Hill said. “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.”
C:C and T:T type horses can be differentiated in the rate of muscle growth and fiber type. A mutation on the ‘Speed Gene’ alters that rate. The study found myostatin to be the most important determinant, but research shows additional genes can have moderate effects on a horse’s distance ability.
The study also notes the demands of the commercial market leads to the breeding of more C:C type horses than T:T type.
“Since there is just one gene that is a major player in the sprinting versus staying stakes, it is extremely vulnerable to selection pressures,” Hill said. “This has been recognized by the concern in the industry over the potential reduction in genetic diversity by favoring precocious, commercially attractive horses.
“This concern is well justified, the staying type is at serious threat of extinction in the global population. T:T (staying) types make up less than 17 percent of elite race winners in Britain and Ireland and less than 7 percent of the Australian elite winning population. This is a complete reversal from the picture of genetics of the Thoroughbred 150 years ago.
“We do not operate our testing services in the sales environment which could further accelerate this trend. However, it is essential that the industry incentivizes the breeding and racing of stayers to reduce the pressure to breed for the sales ring.”