Decreased sperm survivability in subfertile Delaware roosters as indicated by comparative and competitive fertilization.

Duration of fertility following intravaginal and intramagnal insemination of hens with viable spermatozoa from subfertile Delaware roosters was compared with that obtained with spermatozoa from fertile Leghorns and subfertile Wyandotte roosters. In contrast to results with Leghorn and Wyandotte birds, duration of fertility was not increased following intramagnal insemination of spermatozoa from Delaware birds. Competitive fertilization also demonstrated that duration of fertility was less than expected in the spermatozoa from Delaware birds. Heritable subfertility in Wyandotte and Delaware roosters therefore appears to be attributable to distinct sperm defects.