Study On Improvement Of Pregnancy Rate Of Bovine Sexing Embryo Transfer

The aim of this study is to establish an effective system that fit for industrialization in china after factors affectting pregnancy rate were analyzed to improve pregnancy rate. 800 high quality dairy cows were superovulated to produce embryos in Mu Danjiang Longda Ltd.Co of Hei Longjiang province and Xinjiang Jinniu Group. Female embryos transferred or after . Analyzed pregnancy rate of sexed embryo on embryo character, recipient character and their correlativity. The result as follows:1 .In the aspect of embryo of this experiment, both pregnancy rate of nonsexed and sexed embryos were lower as the stage was higher.On nonsexed embryo, there was no significant difference on pregnancy rate of morula-ealy blastocyst and blastocyst , blastocys and expanded blastocyst (P>0.05),but significant at morula-ealy blastocyst and expanded blastocyst(P<0.05) . There was no difference on all stages of sexed embryos(P>0.05). Pregnancy rate on grade 1 was higher than grade 2 of sexed embryo.2.The operation of sexing to embryo affect pregnancy rate of sexed embryo. Regular and sexed embryos were compared between fresh and frozen embryo, the result indicated that the pregnancy rate of regular embryo tend to higher than sexing embryo of fresh or frozen embryo ,but there was no significant difference (P>0.05) .Compared pregnancy rate on fresh and frozen embryos of regular embryos, there was no significant difference(P>0.05),but very significant on sexed embryos(P<0.01).This may due to more damage to sexed embryos after embryos were frozen. Influence of sample size during sexing on pregnancy rate was analyzed. The result indicates that there was no difference on pregnancy rate of fresh and frozen embryos was found between embryos being removed 1-4 cells and 5-10 cells (P>0.05). There was no difference on developmental rate outside in vitro between embryos within 3h and 3-5h from flushing to freezing (P>0.05), but both of them were obviously higher than those embryos from flushing to freezing more than 5 h (P<0.05).3.On the effect to pregnancy rate of season change , the result indicates that There was no significant difference on ET pregnancy rate in different season on the condition of house-feeding . The pregnancy rate of good progenitive capacity cows was higher than the bad progenitive capacity cows and the abort cows (P<0.01). There was no difference on pregnancy rate of multiparity and nulliparity (P>0.05).4. Embryos were collected from the donors after 7.5d±5h in estrus,the redult is indicated that all stages of embyos could get acceptable pregnancy rate when they were transferred to the recipients of 7.5-8.5 days after estrus.The result indicated that to transfer sexing embryo, there is no obvious effect on pregnancy rate of embryo stage and quality(grade 1 and grade 2 ). And when do embryo sexing the cells were being removed from embryo shoud at 5± 1 cells and the embryos kept ouside must be within 5 hours then can get high pregnancy rate. The recipients at 7.5-8.5 days after estrus got better pregnancy rate. There fit for ET in every season in china.