Higher levels of inbreeding in thoroughbreds result in fewer racehorses, according to new research published in the journal Proceedings of the Royal Society B: Biological Sciences.
A study carried out by scientists at University College Dublin, the University of Edinburgh, and the Irish equine science company Plusvital, examined samples from over 6,000 thoroughbred horses from Europe and Australia, and found those animals with the highest levels of DNA-measured inbreeding had a 13% lower probability of ever competing.
Furthermore, the researchers identified in one percent of thoroughbreds two copies of a negative genetic marker linked to bone development and repair. These animals have an increased probability of 32% of never racing.
"The identification of the single genetic marker with a strong negative effect is good news, because it means that it can be managed," said lead researcher Professor Emmeline Hill in a report.
"If the 'carrier' status of a mare and stallion are known, this information can be used to avoid producing foals with two copies of the genetic marker. The immediate benefit of this will be economic gains for breeders and racehorse owners and improved animal welfare. The knowledge of this genetic marker will allow for testing to reduce the negative impact of inbreeding," he explained.
"The effects of inbreeding that we have seen are certainly not new. These results are a warning sign about the rising trend in inbreeding in thoroughbred," said co-author Professor Josephine Pemberton, University of Edinburgh.
Inbreeding in the thoroughbred racehorse has been on the rise with concerns for future population health. However, the identification of this new genetic marker, and the potential to introduce genetic screening, means breeding decisions can be better managed to improve the health and welfare of these valuable animals.
Professor David MacHugh, a co-author on the paper, said: "There is still enough diversity in the gene pool for breeders to proactively manage breeding decisions and use genetically less related stallions. The best way to assess inbreeding and relatedness is through in-depth analysis of DNA variation across horse genomes."
