Parthenogenetic development in-vitro of bovine secondary oocytes exposed to a single electric pulse

Abstract

The effects of CZB and TCM-199 media were compared, with and without conditioning with either bovine oviductal epithelial cells (BOEC) or Buffalo rat liver cells (BRLC), on the cleavage rate, development to the 4- to 8-cell stages and subsequent advancement to morula and blastocyst stages of bovine zygotes. A total of 2122 oocytes were matured and fertilized in vitro and were used in a 2 × 3 factorial, completely randomized block design. Initial cleavage rates were higher (92 vs 83%; P<0.05) and there were more 8-cell embryos produced (62 vs 42%; P<0.01) after 48 hours of culture in CZB than in TCM-199 medium. Conditioned medium provided more 8-cell embryos following 48 hours of culture (56 vs 42%; P<0.01) than unconditioned medium, and fewer 4- and 8-cell embryos subsequently developed to morula and blastocyst (48 vs 76%; P<0.05) in the unconditioned medium. However, effects of BOEC- and BRLC-conditioning were indistinguishable. These data demonstrate the value of CZB over TCM-199 medium in the initial 48 hours of zygote culture, and that media conditioned by either BRLC or BOEC are equally effective at promoting bovine embryo development in vitro. Under optimal conditions, i.e., CZB medium for 48 hours and subsequent culture in TCM-199 with either BOEC or BRLC conditioning throughout, approximately 40% of the oocytes reached the blastocyst stage.