Too few foals and too much breeding interest in specific bloodlines could be leading to reduced genetic diversity in Thoroughbreds raised in countries outside North America and Europe, recent study results suggest. | Photo: iStock

In North America and Europe, both of which have a long racing history, the Thoroughbred population is wide and varied with a strong genetic pool. In Japan and some other countries, however, the sport is relatively new and founded on a limited number of imported horses. While that limited gene pool hasn’t put Asian racehorses at a risk of losing genetic diversity, selective breeding and low foal numbers have, researchers in Japan recently learned.

“As long as the current trend of reproduction continues, the genetic diversity of the Japanese Thoroughbred population will tend to gradually decrease, as we’ve shown it to be doing already over the past decade,” said Hironaga Kakoi, PhD, of the Laboratory of Racing Chemistry, in Utsunomiya, Tochigi.

He and colleagues recently investigated the genotypes of more than 100,000 Thoroughbreds registered in Japan from 2002 to 2016