From Racing to Breeding: Not a Problem for Most HorsesBy Kentucky Equine Research Staff · September 22, 2011
In order to investigate the effect of race training and performance on future breeding success, researchers at the University of Finland examined the records of over 60,000 harness horses, both mares and stallions, that raced and subsequently were retired to breeding careers. The horses were of either Standardbred or Finnhorse bloodlines.
For females, they found that mares with few races got the benefits of training, including good nutrition and care, but did not suffer excessive stress that might lead to low conception rates. Mares with the best racing records tended to get preferential treatment at the track, possibly including better care and a higher plane of nutrition, and these mares also showed the highest foaling rate in their breeding years.
The researchers suggested that owners should plan to retire fillies and mares before rather than in the middle of a breeding season for the best chance of conception. They also warned that older maiden mares are sometimes hard to get in foal, so owners should not wait until racing mares are very old.
In this study, racing stallions showed no effects on fertility after they were retired to stud.