| Multiple ovulation, estrous synchronization and embryo transfer in Tianzhu white yak were studied and applied practically, and also the changes of some important reproductive hormones in serum of donors and recipients during the treatments of superovulation and estrous synchronization were detected. It is hoped that a simple and efficient embryo transter system in Tianzhu white yak will be obtained. And a foundation of quick breeding in Tianzhu white yak could be established theoretically, and a full scale production would be formed. The results were as follows:1. Ten Tianzhu white yaks were treated with an equal dosage of FSH made in China for superovulation, 4 yaks were estrous, of which there were 2 Ganba(Ganba is the local dialect,it means a yak which had her baby the year before last year,and now she has no baby to feed this year.), 1 Yarima(Yarima is a yak which has to feed her baby this year.)and 1 Touma(Touma is a young yak which is going to be her breeding age).The percentage rate of estrous was 40%. After superovulation, the average size of the ovaries of the 4 yaks was (3.8±0.8)×(3.0±1.1)×(2.1±0.6)cm3,and it was 22.47±5.62 times bigger than before. There were 10 corpus luteums on the surface of the ovaries of the Ganba yaks, and the other one Yarima and Touma had 2 and 4 corpus luteum respectively. The other 6 yaks which had no estrous symptoms had several little follicles on the surface of the ovaries, and the size of the ovaries was also bigger than before by 5.73±4.21 times.2. In the control experiment, also 10 Tianzhu white yaks were treated with a descending dosage of FSH made in China for superovulation,of which 5 yaks were estrous and the follicles were developed and ovulated, including 2 Ganba, 2 Yarima and 1 Touma, and the percentage of superovulation was 50%. The size of the ovaries was getting bigger variously. And there were 17 corpus luteum and some developing follicles on the surface of the ovaries.3. In this experiment, ten white yaks were treated with an equal dosage of FSH made in Canada for superovulation,2 Ganba, 2 Yarima and 1 Touma were estrous in 72 hours, and altogether 16 corpus luteums and 4 follicles were found on the ovaries. The percentage of superovulation was 50%. More corpus luteum and number of estrous yaks in Ganba were abtained than those of Yarima and Touma dramatically (p<0.05).4. In the control experiment, 12 white yaks were treated with a descending dosage of FSH made in Canada for superovulation,6 yaks were estrous, and 22 corpus luteum and 9 follicles were detected on the surface of the ovaries.The percentage of the superovulation was 50%.5. In the experiment which was designed to study the effects of high dosage of FSH on the superovulation, 6 yaks were treated, and 3 yaks were estrous. On the ovaries there were 10 corpus lutuems and 4 follicles, and the percentage of the superovulation was again 50%.6. Among the 6 yaks which were treated with PMSG, only 2 were estrous within 96 hours, and 6 corpus luteums and 8 follicles were detected, the percentage of the superovulation was 33%.7. The results of the repeated treatment with CIDR and FSH showed that 4 of 6 yaks were estrous and they had 22 corpus luteums and 5 follicles on the ovaries, and the percentage of the superovulation was 67%, dramatically higher than that of using PMSG(p<0.05). And the size of the ovaries were 23.24±5.11 times than before.8. In the experiment of the estrous synchronization with CIDR and PGF2α,26 black yaks(recipients) were injected with PG which was made in Shanghai, of which 14 yaks were estrous at different time, most of them within 25～72 hours after the injection of PG,the percentage of the estrous synchronization was 53.8%. And 20 recipients were treated with PG made in Ningbo, of which 11 yaks were estrous, the percentage of the estrous synchronization was 55%.9. Forty yaks were treated with PGF2αfor estrous synchronization, and 18 yaks in group 1 were injected PG only once at any stage of reproduction. Four yaks were estrous within 49～120 hours after the injection. And the percentage of the estrous synchronization was 22.2%. In group 2, 22 yaks were treated with two injections of PG at a certain period of time, of which 11 yaks were estrous after the injection, mostly in 25～72 hours. The percentage of the estrous synchronization was 50%.10. In this experiment, 29 yaks were used to recover the embryos. Altogether 128 embryos were obtained, of which 104 were usable and the other 24 were degenerated. The percentage of transferable embryo was 81.3%. Among the 104 usable embryos, 85 were morula, and 19 were early blastula.11. During the period of embryo transfer, 27 recipients were transferred with fresh embryos and 14 were pregnant, the pregnancy rate was 52%. And one pregnant yak died, so 13 new-borns were obtained. And also 13 frozen embryos were transferred to 13 recipients, 5 were pregnant and the pregnancy rate was 38.5%. In this experiment, also 5 fresh embryos and 6 frozen embryos were tranfferred to the black yaks which were estrous spontaneously, 6 yaks were pregnant and the pregnancy rate were 60% and 50% respectively.12. During the period of the superovulation in donors, the concentrations of the serum progesterone had no difference before d8, after that, it decreased dramatically, reaching its minimum level, and then increased again. Those of estrogen changed contrarily during the whole process.13. For the recipient, the changes of serum progesterone and estrogen concertrations during the period of the estrous synchronization were the same as those of the donors, progesterone decreased while estrogen increased at d10 of the process.The results suggested that there were no differences between the treatments on superovulation of donors with FSH whether made in China or made in Canada, and also the number of the corpus luteum were similar between the two methods. And the effects of the superovulation were similar between the equal dosage of FSH and the descending dosage of FSH. Ganba was the most suitable donor for superovulation, It can make more embryos than Yarima and Touma can do. On the same conditions, the effects of superovulation on the donors whether with ordinary dosage or with high dosage were almost the same, and the percentage of of the estrous yaks and corpus luteum were also similar. The effect of superovulation treated with PMSG was lower than that of FSH, and the average size of ovary was also smaller. The effect of superovulation of repeated treatment was higher than that of single treatment dramatically, and so was the number of the corpus luteum. In the experiment of estrous synchronization, the source of PG has little effects on estrous synchronization (P>0.05). At any stage of reproduction, a single injection of PGF could only have a 22.2% estrous synchronization rate, but two injections of PGF can have much higher percentage at 50% (P<0.05). The percentage of estrous synchronization with CIDR and PGF is higher than that of estrous synchronization with PGF only(P<0.05), but has no differences comparing with using PGF twice. There are 128 embryos attained from 29 white yaks treated with superovulation. And the average is 4.41 embryos. In these 128 embryos, 104 are transferable. The morula and early blastula are 81.7% and 18.3% respectively. Pregancy rate of the recipient transferred with fresh embryos is higher than that of frozen embryos. And also that of spontaneous estrous animals is much higher than that of animals treated with hormones. Improving the nutrition of the recipients and reducing the stress can increase the pregnancy rate evidently. During the superovulation of the donors and the estrous synchronization of the recipients, the changes of several steroids in serum are similar between the donors and the recipients. It shows that the donors and the recipients are in the same reproductive stage. |
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