Effects of Different Freezing Methods and Thawing Solutions on Boar Semen Cryopreservation Efficiency

Three different methods were applied to freeze boar fresh semen and two kinds of thawing solution were used to thaw the frozen sperm.The optimal freezing method and thawing solution for boar semen cryopreservation were identified based on the motility of thawed sperm and the percentage of sperm with integrity acrosome.In experiment 1:Three health and fertile boars were used for semen collection.The fresh semen was frozen by three different methods(dry ice/pellet,liquid nitrogen/pellet and liquid nitrogen/straw).The sperm motility and the percentage of sperm with integrity acrosome were compared after thawing in same way.In experiment 2:The frozen sperm was thawed with different thawing solutions and the sperm motility and acrosome integrity were compared.In experiment 3:Based on experiment 1 and 2,the sperms frozen-thawed by the best freezing method and thawing solution were selected for in vitro fertilization experiment.The development of IVF embryos derived from frozen sperm were investigated with IVF embryos derived from fresh sperm and parthenogenetic embryos as control.Results were as following:1,The motility of sperm frozen by dry ice/pellet(0.23) was higher than that by liquid nitrogen/pellet(0.20),after thawing.Both of them were significantly higher than that(0.08)by liquid nitrogen/Straw(P0.05).The percentage of sperm with integrity acrosome in dry ice/pellet group(58.0%) was significantly different from that in liquid nitrogen/pellet group(54.7%) and liquid nitrogen nitrogen/straw group(54.2%),but there were not significant difference between liquid nitrogen group and liquid nitrogen/straw group(P0.05).2,The motility of sperm thawed by a high glucose-EDTA solution(0.22)was significantly higher than that by a PBS-BSA solution(0.13)(P0.05).3,The sperm frozen by dry ice/pellet method and thawed in high glucose-EDTA were used for IVF.The results indicated that there was no significant difference in blastocyst formation between frozen semen(17.6%)and fresh sperm(17.9%),but both of them were significantly lower than parthenogenetic activation(36.6%)(P0.05).A conclusion can be drawn:The dry ice/pellet might be the appropriate freezing method and high glucose-EDTA might be the appropriate thawing solution for boar semen cryopreservation.The frozen sperm derived embryos showed same blastocyst formation potential compared with fresh sperm derived embryos.