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The Relationship Between Sperm Hydrolysis of the Perivitelline Layer and Embryonic Livability

College of Agriculture and Life Sciences, Department of Poultry Science, North Carolina State University, Raleigh, North Carolina 27695-7608

Correspondence: V. L. Christensen, E-mail: vern_christensen{at}ncsu.edu

The hypothesis was proposed that altered sperm hydrolysis of the germinal disc area of the ovum affects embryonic survival. Genetics and damaged spermatozoa were the 2 factors tested. Both factors affect embryonic livability. The mechanism of sperm selection was proposed to be in the oviduct or at the ovum during fertilization. To test the hypothesis, sperm hydrolysis from the creation of holes in the perivitelline layer and embryonic mortality were compared in 3 lines of turkeys representing the past 50 yr of turkey genetics. In the newer lines compared with older, sperm hydrolysis decreased and embryo livability at the first week of embryonic development declined, but embryo livability during the fourth week improved. The same lines were inseminated with 0- or 24-h-stored semen. Although penetration of the perivitelline layer by fresh sperm cells declined in modern lines, penetration of 24-h-stored sperm cells did not. When inseminated with 24-h-stored semen, all 3 lines showed depressed embryo livability compared with fresh semen at wk 1 of embryo development but improved embryo livability at wk 4 of development. In experiment 2, specific comparisons of single-trait selected lines with unselected control lines indicated that selection for rapid growth has increased sperm hydrolysis of the perivitelline layer by 24-h-stored sperm, but selection for increased egg production has not. In vitro sperm hydrolysis of the perivitelline layer was examined only for the growth-selected line in experiment 3. The in vitro technique was used to examine perivitelline layer hydrolysis without oviduct effects. The data indicated no differences in holes in the perivitelline layer for lines or sperm storage. Thus, the data suggest that a reduction in the penetration of sperm through the perivitelline layer results in improved embryo livability at wk 4 of development, but we saw no association with wk 1 embryo livability.

Key Words: sperm hydrolysis • embryo viability • fertility • turkey