Abaxial tail attachment of bovine spermatozoa and its effect on fertility.

The prevalence of abaxial sperm tails, accessory tails and double tails, was determined from semen evaluation records of 600 western Canadian range bulls and 449 bulls in Canadian artificial insemination centers. Spermatozoa with abaxial tails were produced by 10.5% of bulls, however, only 0.48% produced sperm with greater than 50% abaxial tails, and 0.86% of the 1049 bulls produced sperm with accessory and double tails. Three experiments were done to determine the importance of abaxial sperm tails to fertility. In experiments 1 and 2, frozen semen with 88%, 50% and 0% abaxial tails was used to inseminate synchronized heifers, which were allowed to develop pregnancy, and superovulated heifers, which were slaughtered prior to embryo recovery seven days after breeding. In experiment 3, a bull which produced 100% abaxial sperm was used in a competitive mating situation with three control bulls in a herd of 118 cows. The combined results of these experiments indicate that spermatozoa with abaxial tail attachment fertilize ova at a normal rate and are not associated with any increase in embryonic death.