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Concern over inbreeding levels in racehorses

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(Stock picture)

(Stock picture)

(Stock picture)

Concerns have been raised over a significant rise in inbreeding levels in racehorse population over the last 45 years.

New research by scientists at University College Dublin and equine science company Plusvital has established linked the increase in inbreeding to selection for favourable racing traits and the influence of popular sire lines – 97pc of horses in the study traced to Northern Dancer, and 35pc and 55pc of European and Australian horses had Sadler’s Wells and Danehill, respectively, in their pedigrees.

Selection for popular sire lines reduces genetic diversity which can lead to inbreeding depression.

The research, published this week in the peer-reviewed journal Scientific Reports, analysed the genomes of over 10,000 thoroughbreds, the largest set of horses examined to date.

UCD Professor in Equine Genomics, Emmeline Hill said in breeding has always been high in Thoroughbreds, but it is getting higher.

"It is likely that, unchecked, inbreeding in the Thoroughbred will continue to increase in a market where there is high demand for particular sire lines.

"The problem with inbreeding is that it can compromise overall population fertility and health," she warned.

Unlike most managed animal production systems, there is no systematic, industry-mediated genomic selection or population management for the Thoroughbred.

“Pedigree is not powerful enough to help any more. Pedigree can be useful in highlighting broad trends in breeding practices, such as the predominance of certain sire lines leading to a high degree of relatedness. However, since

"Thoroughbreds are now so closely related, there is no longer the resolution in a pedigree to accurately infer relatedness between individuals,” said Professor Hill.

Higher inbreeding is not associated with superior racing performance, and Professor Hill reiterated that the research should be seen as a positive for the industry.

“The purpose of this research is to provide information that, if harnessed in the appropriate way, could be beneficial to ensure the future sustainability of the breed.”

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