Survey of reproductive efficiency in the Quarter-horse and Thoroughbred.

Reproductive efficiency was evaluated for 838 Quarter-horse mare-years on five farms and 939 Thoroughbred mare-years on seven farms over 4 years. The pregnancy rate from first service was 51% for Quarter-horse mares and 43% for Thoroughbred mares (P less than 0-05). The cumulative pregnancy rate after five services was 85% for Quarter-horse and 77% for Thoroughbred mares (P less than 0-05). First-service-period pregnancy rates were 44, 40 and 54% for maiden, barren and foaling mares, respectively. Cumulative pregnancy rates after five service-periods were 84, 74 and 84% for maiden, barren and foaling mares, respectively. The pregnancy rate for foaling mares served during foal heat was lower (P less than 0-05) than the first-servicd pregnancy rate of foaling mares served after the foal heat. Less than 40% of the maiden mares, less than 50% of the barren mares and less than 30% of the foaling mares were submitted for their first-service-periods by the end of March.