SUMMARY
Soy bean lecithin has been attracted increasing attention and has been used to ‎substitution egg yolk in the semen extender. Aim of the current paper was to study the ‎impact of substitution of egg yolk with soybean-lecithin in tris-extender on freezability ‎and fertilizing capacity of Holstein sperm in post-thawed semen. Semen from five ‎Holstein bulls was frozen in tris-citric acid extender containing 15% egg yolk (EY, ‎control) or 0.25, 0.5 and 0.75% soybean-lecithin (SBL). Percentages of motility, ‎livability, plasma membrane integrity and intact acrosome spermatozoa were assessed in ‎diluted, equilibrated and thawed semen. Results showed that 0.5% SBL-extender had ‎positive (P<0.05) effect on percentages of motility, livability, plasma membrane integrity ‎and intact acrosome of sperm cells after dilution, equilibration and thawing. In post-‎thawed semen, the highest (P<0.05) sperm recovery rate of motility, livability, plasma ‎membrane integrity and intact acrosome was obtained for 0.5% SBL-extender compared ‎to others extenders. The highest conception rate (68.6%) of Holstein cows was obtained ‎following insemination with semen extended with 0.5% SBL compared with other ‎extenders (48-56%).‎
In conclusion, egg yolk could be substitution by soybean-lecithin in tris-based ‎extender at a level of 0.5% to improve fertilizing capacity of cryopreserved Holstein ‎semen. ‎