| [Objective] To evaluate the effect of embryo quality and developmental stages on pregnancy rate in recipients. [Method] 63 dairy heifers were superovulated and the quality and developmental stages of collected embryos were evaluated. 334 embryos in the compact morula, early blastocyst,blastocyst and expanded blastocyst stages that were of grade A,B and C quality levels were transferred to the recipients. Data of embryo production,embryo quality distribution, developmental stages distribution and the pregnancy rates on days 30 were analyzed. [Result] In transferable embryos, the proportion of grade A embryos (60.78%) was significantly higher than the proportion of grade B and C embryos (36.70% and 2.52%) (P<0.05).The proportion of compact morula (54.36%) was significantly higher than the proportion of early blastocyst, blastocyst and expanded blastocyst (18.35%, 25.0% and 2.29%) (P<0.05).On day 30,the pregnancy rate of grade A and B embryos (63.55%, 64.35%) were significantly higher than the pregnancy rate of grade C embryos(44.44%)(P<0.05). There were no significant difference on the pregnancy rate of compact morula,early blastocyst,blastocyst and expanded blastocyst (60.75%,66.67%, 67.86% and 60.00%) (P>0.05).[Conclusion] The selection of grade A and B embryos with different embryonic developmental stages can ensure efficient of embryo transfer. Increasing the number of early blastocysts and blastocyst transfers can improve embryo transfer pregnancy rates. |