The thoroughbred industry can thank a single shetland pony mare that lived about 300 years ago for providing the breed’s impressive speed, research suggests.
Scientists have traced the origin of the so-called “speed gene” in thoroughbreds back to a single British mare that lived in the United Kingdom about 300 years ago.
The findings were published today in the scientific journal, Nature Communications.
The origin of the “speed gene” – formally known as the C type myostatin gene variant – was revealed by analysing DNA from hundreds of horses, including DNA extracted from the skeletal remains of 12 celebrated thoroughbred stallions born between 1764 and 1930.
“Changes in racing since the foundation of the thoroughbred have shaped the distribution of ‘speed gene’ types over time and in different racing regions,” said Dr Emmeline Hill, the senior author of the study.
“But we have been able to identify that the original ‘speed gene’ variant entered the thoroughbred from a single founder, which was most likely a British mare about 300 years ago, when local British horse types were the pre-eminent racing horses, prior to the formal foundation of the Thoroughbred racehorse,” said Hall, a genomics scientist at the School of Agriculture and Food Science at the University College Dublin.
The researchers traced all modern variants of the original speed gene to the legendary Nearctic (1954-1973), and attribute the wider expansion of these variants to Northern Dancer (1961-1990), the son of Nearctic, and one of the most influential stallions of modern times.
“Having first identified the ‘speed gene’ in 2010, we decided to see if we could trace the origin of the gene variant using population genetics coupled with pedigree analysis,” Hill said. “We wanted to understand where speed in the thoroughbred came from.
“We traced the economically valuable gene variant by determining ‘speed gene’ type in almost 600 horses from 22 Eurasian and North American horse breeds, museum bone and tooth specimens from 12 legendary thoroughbred stallions, 330 elite performing modern thoroughbreds from three continents, 40 donkeys and two zebras.”
According to co-author, Dr Mim Bower, from the University of Cambridge: “The findings point to a British mare as the most likely single founder of the original ‘speed gene’ because one of the lines of evidence from the research demonstrated that the prize stallions of the 17th and 18th centuries had two copies of the T type speed gene variant (T:T) which is linked to greater stamina.
“At this time in the history of horse racing, races were between two horses competed over multiple heats, at distances of between two to four miles, and repeated until a horse had won the event twice or ‘distanced’ the opponent,” Bower said.
“Horses did not race until they were five or six years old, and then only two or three times in their lives. This is consistent with these horses being T:T types.”
An increased premium on speed and early development arose as two-year-old races became popular during the last century, and in many regions of the world, these preferences remain to this day.
Hill explained: “For example, in Australia, the myostatin ‘speed gene’ type (C:C), which is best suited to fast, short-distance, sprint races, is more common and there is a market-driven demand for horses with at least one copy of the C-type gene variant.
“This just goes to show the power breeders have to shape the genetic make-up of their horses.
“Decisions regarding the race pattern in each racing jurisdiction and the commercial demand for certain types will also rapidly influence the genetic make-up of the population.”
To identify where the C-type gene variant originated, the researchers analysed DNA samples from more than 20 horse breeds that included representatives of local British and Irish horses, from where female thoroughbred lineages derive, and exotic eastern populations from where male thoroughbred lineages derive.
The study identified the Shetland breed as having the highest frequency of the C-type gene variant. The Shetland represents local British horse types, which were the pre-eminent racing horses prior to the formal foundation of the thoroughbred.
By comparing the diversity of the chromosomes around the C and T-type gene variants, researchers found only a single C-type compared to 11 different T-type gene variants, meaning that the speed gene entered the thoroughbred just once.
“The results show that the ‘speed gene’ entered the thoroughbred from a single founder, which was most likely a British mare about 300 years ago when local British horse types were the preeminent racing horses, prior to the formal foundation of the thoroughbred racehorse,” Hill said.
Collaborators in the study were scientists from Trinity College Dublin, the Russian Academy of Sciences and the Swedish University of Agricultural Sciences. The research was supported by grants from The Horserace Betting Levy Board, Leverhulme Trust, Cambridge Overseas Trust and Science Foundation Ireland.
Hill is a co-founder of Equinome, a University College Dublin spin-out company, which has developed The Equinome Speed Gene Test.
This test is currently being used to identify the optimum racing distance for individual thoroughbred horses.