Dam and Sire Effects on Sperm Penetration of the Perivitelline Layer and Resulting Fecundity of Different Lines of Turkeys

All birds studied thus far are able to store spermatozoa within their oviducts for periods that can vary from several days to weeks, depending upon the species. Turkeys have a relatively long storage period compared with chickens, an observation that leads to the suggestion that sperm residing within the oviduct may interact with sperm entering the oviduct from later inseminations. Multiple sources of sperm within the oviduct also lead to the hypothesis that sperm competition may be important for the maintenance of fertility and embryo livability in turkeys. The current study tested the hypothesis that selection for economically important traits in lines of turkeys may have an effect on sperm competition as measured by the ability to hydrolyze holes in the perivitelline layer, fertilize, and produce viable offspring. Lines of turkeys selected for egg production or rapid growth were compared with their respective randombred control lines. Reciprocal crosses of dams and sires of the selected and control lines were made to determine inherent sire and dam roles in sperm competition. Selection for increased egg production increased hydrolysis of the perivitelline layer and improved fertility but decreased early embryo death while increasing embryo deaths at pipping compared with controls, and these effects were primarily determined by the dam. Selection for increased body weight has created an interaction between dams and sires for sperm hydrolysis of the inner perivitelline layer, fertility and embryo survival. Thus, we concluded that genetic selection for economically important traits may affect sperm hydrolysis of the perivitelline layer and the subsequent fertility, and embryo livability.