Inbreeding in Thoroughbreds: Positives and Negatives

Selective breeding has led to a Thoroughbred uniquely adapted to modern racing’s demands. But it’s also led to inbreeding, and with that has come some less favorable genetic issues.

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inbreeding in Thoroughbreds
The Thoroughbred breed was founded and has since been selectively bred for the purpose of elite racing performance. While this has led to inbreeding and some less favorable genetic traits, breeders have done comparatively well in maintaining genetic diversity in the breed, Todd said. | Photo: Jeff Kubina/Wikimedia Commons

Three hundred years of selective breeding has led to a modern Thoroughbred that performs highly in his specific field and conditions. But it’s also led to inbreeding, and with that has come less favorable genetic issues, Australian researchers say.

An analysis of data from more than 135,000 Thoroughbreds racing in Australia from 2000 and 2010 has shown that inbreeding has failed to “alleviate the genetic load” in the breed and possibly put it at a higher risk of developing heritable health problems, said Evelyn Todd, a PhD candidate in the University of Sydney School of Life and Environmental Sciences.

That means Thoroughbreds around the world continue to carry genetic traits that could lead to heritable health problems, Todd said. While all individuals have some risk of such issues, a greater level of inbreeding increases the risk of them occurring

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Passionate about horses and science from the time she was riding her first Shetland Pony in Texas, Christa Lesté-Lasserre writes about scientific research that contributes to a better understanding of all equids. After undergrad studies in science, journalism, and literature, she received a master’s degree in creative writing. Now based in France, she aims to present the most fascinating aspect of equine science: the story it creates. Follow Lesté-Lasserre on Twitter @christalestelas.

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