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S. Iwasaki, N. Yoshiba, H. Ushijima, S. Watanabe, and T. Nakahara

Summary. The morphology and proportion of inner cell mass (ICM) of bovine blastocysts cultured in vitro or in vivo in rabbit oviducts after in-vitro fertilization of in-vitro matured follicular oocytes were compared with those of blastocysts fertilized in vivo by a differential fluorochrome staining technique. The delineation of each ICM cell was improved by the transfer of embryos derived from in-vitro fertilization to a rabbit oviduct although the cell–cell contacts of ICM cells were not as tight as those from in-vivo fertilization. The proportions (15·8 and 14·9%) of ICM in blastocysts cultured in vitro at early and expanded stages were significantly lower than those cultured in rabbit oviducts after in-vitro fertilization and fertilized in vivo. These results show that the transfer of bovine embryos derived from in-vitro fertilization to the rabbit oviduct increased the proliferation of ICM cells to the level of embryos fertilized in vivo although the cell–cell contact of ICM cell is not improved by the process.

Keywords: cattle; blastocysts; inner cell mass; in-vitro fertilization

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T. Nagai, T. Takahashi, H. Masuda, Y. Shioya, M. Kuwayama, M. Fukushima, S. Iwasaki, and A. Hanada

Summary. In Exp. 1 pig oocytes matured in vitro were used to evaluate the fertilizability in vitro of frozen epididymal (4 boars) and ejaculated (3 boars) spermatozoa that were preincubated in modified TCM-199 for 4 h at 37°C. The percentages of penetrated oocytes with the frozen epididymal spermatozoa were 0–40%. In contrast, none of the occytes were penetrated with the frozen ejaculated spermatozoa. In Exp. 2, oocytes matured in vivo were inseminated in vitro with the frozen epididymal spermatozoa that were known to penetrate oocytes matured in vitro. The penetration rate was 79% and the percentage of polyspermic oocytes was 57%. Culture for 30 h of oocytes matured in vivo and fertilized in vitro resulted in 51% (34/67) developing to the 2-cell stage. These embryos were transferred to 2 recipient gilts. One gilt became pregnant and a litter of 3 (1 live and 2 dead) was born. These results indicate that frozen epididymal spermatozoa can be used for in-vitro fertilization in the pig.

Keywords: in vitro; oocyte; fertilization; pig; embryo transfer