Differential Effect of Medium on the Ratio of ICM/TE of Bovine Embryos in a Co-culture System

Background: This study was undertaken to investigate the efficiency of two different embryo somatic cell co-culture conditions, tissue culture medium 199 (TCM199)-vero cells and Menezo B2 (B2)-vero cells, for the in vitro developmental quantity and quality of bovine embryos. Materials and Methods: Bovine oocytes were allowed to mature and subsequently undergo fertilization in vitro. Their presumptive zygotes were cultured in either TCM199 or B2 culture media in conjunction with vero cells for up to nine days. The culture media were refreshed every two days and the proportion of embryos that cleaved and further developed to the morula and blastocyst (early, expand and hatched) stages were recorded. Hatched blastocysts underwent differential staining in order to determine the numbers of inner cell mass (ICM) and tropho ectoderm (TE) and total cell number (TCN). Results: Of the two groups, no significant difference was seen between the proportions of the presumptive zygotes cleaved, those which developed to 8-16 cells, morula and reached days 7or 8 blastocyst stage or hatched. However, the values for TCN and TE of the TCM199- vero embryos were significantly greater than those of B2-vero embryos. The values for ICM/ TCN and ICM/TE were significantly greater in the B2-vero group versus the TCM199-vero group. Conclusion: Both TCM199 and B2 culture media in conjunction with vero cells were of the same efficiency when used for in vitro development of bovine presumptive zygotes. However, TCM199 was superior in providing embryos with more embryo cell numbers, whereas B2 medium was superior in providing embryos with greater ICM/TE and ICM/ TCN ratios.