| Bovine embryos transferred includes estrus synchronization of donor and recipient,superovulation and transfer. The bottleneck which is low pregnancy rate and high cost restrict development of embryo transfer. For solving the difficulty of embryo transfer, this research was conducted on the pivotal technique of embryo transfer, to advance using rate of donor and recipient,reduce cost and accelerate industrialization spread on embryo transfer.In the experiment, to discuss the effect of repeated superovulation, we had superovulated repeatedly for seven times which have a 20-30 day interval between them on twenty one Simmentals. The effective rate of the first and second superovalation was 95% and 95.2%, respectively, and 100% for the others. According to the number of the collected embryos and transferable embryos, the best effect of superovulation was the third treat, they showed no significant difference in initiatory five times (P＞0.05). Although there is excellent effective rate of superovalation on the sixth and seventh treat, they had an obvious decrease on the collected embryos and transferable embryos. In comparison between the initiatory five times, they showed significant difference (P＜0.01). With the increase of superovulation times, the percentage of grade A embryos descended, but no significant differences between them in the initiatory four treats (P＞0.05). In comparison with the initiatory four times, the results of the fifth superovulation had a significant difference (P＜0.01). The percentage of grade B embryos increased obviously, which was the highest for 57.29% (P＜0.01). According to the number of the transferable embryos of the first treat, we parted the donors into three groups which were 1-4 embryo group, 5-7embryo group and more than 8 embryo group. In comprison between the third group and the other groups, there were significant differences except the first treat(P＜0.01). The average transferable embryo of the first and second time treat was 4.70 and 6.80 in the first group, respectively, there were significant differences (P＜0.05). The average transferable embryo of the first and second group was 4.70 and 8.18, respectively, they had a significant increasing (P＜0.01). When the donors which had been superovulated three times were transferred with embryos, 47.83% pregnancy rate were obtained, no-superovulated pregnancy rate was 58.33%, and that of the regular recipients was 45.16%. there was no significant difference (P＞0.05).In two methods of estrus synchronization, the available rate of recipients was 76.59% and 69.78%, respectively, for CIDR-PG group and one PG injection group. There were significant difference (P＜0.01). In the following experiment, each male embryo that was sexed was split into four symmetrical masses, and each embryo was co-transferred with one mass ,two masses, three masses or four masses, respectively, or each embryo was co-transferred with a parthenogenesis embryo. The results indicated that one mass group had the best pregnant rate of 58.33%, although higher than that of the control group(47.13 %), but there was no significant difference. The pregnant rate of two mass group was lower than that of the control group, but no significant difference was found. The pregnancy rate of parthenogenesis embryo group was 61.36%, which was significantly higher than the control group (P＜0.05) . The parthenogenesis embryo group had better effect than one mass group, but no significant difference was found. In the north of Hebei province, the pregnancy rate of recipients was 51.25 % in October, and it is higher than in June or in July(41.70%, P＜0.05). The pregnancy rate in December was the lowest (37.45%). There were the best pregnancy rate of 52.74% for early blastocysts of regular embryos, which was higher than that ofmorulae and blastocysts (P＜0.01). Early blastocysts had the highest pregnancy rate of 58.09% on the recipients that were on the 8th day after estrus, but there were no significant differences in comparison with the recipients that were on the 7th ,7.5th and 8.5th day after heat. The pregnancy rate of recipients that were transferred double semi-embryo and an intact embryo was 56. 25 and 55.56%, respectively, The parturition rate of recipients was 75.00%和55.56%, respectively, because of very few samples, so there was no significant difference in statistics (P＞0.05).Through the research of repeated superovulation,available rate of estrus synchronization recipients and improvement of pregnancy rate of embryo transfer, we had gained a series of reliable conclusions which have an important meaning to advance the available rate of donor and recipient. |
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