Vitrification Of Bovine Oocytes And Embryo Transfer Of Cryopreserved Embryos To Yellow Cattle

This paper includes two parts of research, vitrification of bovine oocytes and embryo transfer of cryopreserved embryos to yellow catties, the results were shown as follows:1. Vitrification of Bovine OocytesBovine oocytes cultured in vitro for 22h were respectively vitrified in Dimethylsulfoxide (DMSO) or Ethylene glycol (EG) solutions by OPS or straw, after thawing, they were cultured for another 2h and parthenogenetically activated. Experiment 1: In vitro matured bovine oocytes were vitrified by straw or OPS in DMSO+EG solution. Similar morphologically normal and cleavage rates obtained for both vitrified by straw and OPS (90.6% versus 83.2%, 32.3% versus 25.2%, P>0.05 ). Experiment 2: In vitro matured bovine oocytes were first exposed to 4%EG for 15 minutes or to 10%EG for 10 minutes, then they were put into vitrification solution containing 35%EG, 5%PVP, and 0.5Msucrose. Significantly higher rates of morphologically normal and cleavage pretreated with 4%EG than those with 10%EG(79.4% versus 62.2%, 26.5% versus 10.5%, P<0.05). Experiment 3: In vitro matured bovine oocytes were vitried in DMSO+EG or 35%EG by open pulled straw method. There were no differences between two vitrification solutions in morphologically normal and cleavage rates(83.2% versus 79.4%, 25.2% versus 26.55%, P>0.05). In conclusion, bovine oocytes can be vitrified efficiently in DMSO+EG or 35%EG using straw or OPS. Bovine oocytes pre-equilibrated in 4% ethylene glycol solution have better effect than in 10% ethylene glycol solution.2. Embryo Transfer of Cryopreserved Embryos to Yellow Cattle.Two different estrus synchronization methods were used in yellow cow synchronization. Group l:Recipients were administered once 0.6mg PGF2a Group 2:Yellows cows were first injected 0.6mg PGF2a, 9 days later ,they were injected 75ug LHRH-A~3 followed by injection of 0.6mg PGF2a 7 days later and a second 75ug LHRH-A3 administered 48h later. Results shows that there were no difference of estrus and recipient rates between group 1 and group 2(60.0% verse 63.2%, 26.7% verse 36.8%, P>0.05),the pregnancy rate of group 2(28.6%) is higher than that of group 1(0) (P<0.05).In conclusion, interval injection of GnRH/PG is a better method of estrous synchronization.