Successcul embryo transfer of cryopreserved and in-vitro fertilized rabbit oocytes

In-vitro fertilization experiments with frozen/thawed rabbitoocytes were performed to develop an effective technique tobe used for the in-vitro fertilization of cryopreserved humanoocytes. Ovulatory oocytes, colected from the oviduct of virgindoes 13 h after induction of ovulation by HCG injection, werecryopreserved slowly to –30°C and plunged directlyinto liquid nitrogen. A mixture of 1.5 M 1, 3-propanediol and0.1 M sucrose was used as a cryo-protectant. After thawing,the oocytes were incubated with in-vitro capacited sperm for5 h indefined Brackett's medium. Fertilized ova were culturedfor an additional 20 h until the 4-to-8-cell stage was reached.These embryos were transferred to pseudopregnant recipient rabbitswhich were ’asychronous‘ in the sense that theyhad been given an injection of HCG 30, 24 and 18 h before startingto do the embryo transfer. A 32% survival rate of frozen/thawedoocytes was achieved. The fertilization rate was 74% (181/264)in this study. A total of 53 embryos was transferred to theoviducts of six recipients of three different asynchronicityand four young were born. The highest implantation rate (includingresorptions) of 18% could be achived in this investigation byusing –6 h asynchronous recipients, While the overallimplantation rate was 9.4 %