The Comparison Between The Effects Of Frozen-thawed Sheep Embryo Transfer By Programmed Freezing Method And Vitrification Method

This study was trying to establish a set of effective sheep superovulation program and a system to improve pregnancy rate of recipient ewe.we used superovulation,artificial insemination,embryo treatment on black Suffolk sheep to get fresh embryo in Akesu,Xinjiang.We did freezing test,comparison and analysis of factors of thawed embryo transfer pregnancy rate and litter size effect of fresh embryo transfer and the influence of imported program freezing and vitrification of recipient ewes.Experiment 1 The Effect of Donors’ Ages on SuperovulationThe experiment was to investigate the effect of donors’ ages on superovulation in the black Suffolk sheep in Akesu.The results showed that when the three groups of donors at different ages were superovulated by the same drugs in the same way,the superovulation effect between Group 1.5~2 and Group 3~4 years old sheep was significantly different(P < 0.05),and the superovulation effect between Group 3~4years old and 5~6 years old sheep was significantly different(P < 0.05).However,the superovulation effect in Group 3~4 years old and 5~6 years old sheep was higher than that of Group 1.5~2 years old sheep(P < 0.05).The levels of available embryos were compared among the three groups of sheep,the superovulation effect of achieving grade A embryos between Group 1.5~2 and Group 3~4 years old sheep was significantly different(P < 0.05).The superovulation effect of achieving grade A embryos between Group 3~4 and Group 5~6 years old sheep was significantly different(P < 0.05).Experiment 2 The Comparison of Conception Rate and Lambing Rate between Two Kinds of Frozen EmbryosIn order to investigate the effects of frozen-thawed embryo transfer by two different freezing methods on conception rate,we took 471 sheep as recipients by fresh embryo transfer,210 sheep by programmed freezing embryo transfer and 26 sheep by vitrification embryo transfer.The results showed that the conception rate between freshembryos and frozen-thawed embryos was significantly different(P < 0.05),the effect of frozen-thawed embryo transfer by two different freezing methods on conception rate and lambing rate was compared.The results showed that the conception rate in Group vitrification and Group programmed freezing were respectively 58% and 49.5%,significant different(P < 0.05).In order to investigate the effects of frozen-thawed embryo transfer by two different freezing methods on the lambing rate,we made statistics on the lambing.104 in the Group programmed freezing were pregnant and 86 lambs were delivered.14 in the Group vitrification were pregnant,and 13 lambs were delivered.The results showed that the lambing rate of embryo transfer in the Group vitrification and Group programmed freezing were respectively 92.9% and 82.7%,significant different(P < 0.05).Experiment 3 Effects of Recipient Factors on Fresh Suffolk Embryos and Frozen-thawed Dorper Embryos TransferIn this experiment,the data of an experiment on fresh Suffolk and frozen Dorper embryos transfer in Xinjiang were analyzed retrospectively,and the effect of recipient factors on embryo transfer was discussed.The results demonstrated that when embryos were transferred to the recipient ewes on the 7th day after estrus,the lambing rate of frozen Dorper embryos which were in morula stage was significantly higher than those in blastocyst stage after transfer.Under this experimental condition,there was no significant effect on the lambing rate between the different groups divided by the developmental stage or the quantity of fresh Suffolk embryo transferred.The number of previous surgical operations of the recipient sheep had significant effects on the lambing rate of fresh Suffolk embryo transferred,and the lambing rate of the recipients which had surgical operations more than once was significantly lower than those which had no operation experience.When there were more than one corpus luteum in the ovaries of the recipients,the number of ovarian corpus lutea had no significant effects on the lambing rate.