Increased inbreeding reduces the racing performance of Thoroughbred horses

19 April 2018

A scientific study conducted by researchers at the University of Sydney has uncovered breeding strategies to improve the athletic success of Thoroughbred racehorses.

Researchers have found that horses with higher levels of inbreeding, on average, exhibited reduced athletic ability. Thoroughbred horses are bred for the purpose of racing. Horses with greater athletic abilities are able to win more races and earn more prizemoney.

Inbreeding, which is the mating of related individuals, is used in domestic animal breeding to select for desirable traits. However, it can also lead to reduced health. Thoroughbred horses are not as inbred as many other domestic animal populations. But, some inbreeding between individuals with superior athletic success is necessary to select for racing performance.

This study has also found that the slow pace of inbreeding over many generations has successfully selected for genes that have improved the overall athletic performance of the population. PhD student Evelyn Todd, who led the research, said: "These results show that although some inbreeding between horses with superior racing performance may be beneficial, close inbreeding events should be avoided where possible".

This study analysed the racing performance and pedigree records of over 135,000 horses.

The Thoroughbred horse population is unique in that every contemporary individual traces its ancestry back to the 18th century, when the breed was founded. The researchers discovered that some of these founding horses have variable influences on the racing success of their contemporary descendants. Remarkably, inbreeding to one founder, Herod (born 1758), has increased the athletic ability of his modern descendants.

This research provides important information for the Australian Thoroughbred breeding industry, which makes a significant contribution to the economy.

The findings have been published in the journal Scientific Reports.

Contact: Evelyn Todd, PhD Student, School of Life and Environmental Sciences

Email: 2940011b12196a4c25001312021c512a1332642d2d266c591c