EFFECTS OF CZB VERSUS MEDIUM 199 AND OF CONDITIONING CULTURE MEDIA WITH EITHER BOVINE OVIDUCTAL EPITHELIAL-CELLS OR BUFFALO RAT-LIVER CELLSON THE DEVELOPMENT OF BOVINE ZYGOTES DERIVED BY INVITRO MATURATION-INVITRO FERTILIZATION PROCEDURES

The effects of CZB and TCM- 1 99 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 t he 4- to 8-cell stages and subsequent advancement to morula and blasto cyst stages of bovine zygotes. A total of 2122 oocytes were matured an d fertilized in vitro and were used in a 2 x 3 factorial, completely r andomized 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<0.0 1) after 48 hours of culture in CZB than in TCM-199 medium, Conditione d medium provided more 8-cell embryos following 48 hours of culture (5 6 vs 42%; P<0.01) than unconditioned medium, and fewer 4- and 8-cell e mbryos subsequently developed to morula and blastocyst (48 vs 76%; P<0 .05) in the unconditioned medium. However, effects of BOEC- and BRLC-c onditioning were indistinguishable. These data demonstrate the value o f CZB over TCM-199 medium in the initial 48 hours of zygote culture, a nd that media conditioned by either BRLC or BOEC are equally effective at promoting bovine embryo development in vitro. Under optimal condit ions, 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.