The present study was to investigate if a completely chemically defined medium (PZM-4) could support the early development of porcine embryos derived from parthenogenetic activation (PA) and cloning (somatic cell nuclear transfer, SCNT), and to lay the foundation for determining the physiological roles of certain supplements in this medium. Porcine embryos derived from PA and SCNT were cultured in media: PZM-3 (a chemically semi-defined medium), PZM-4 (a fully defined medium), and PZM-5 (an undefined medium). Early embryo development was observed. We found that the three medium groups (PZM-3, PZM-4 and PZM-5) exhibited no significant differences in cleavage rates of PA embryos (p > 0.05), while the blastocyst rate in PZM-3 was significantly higher than in PZM-4 and PZM-5 (78.9% vs. 36.0% and 52.3%) (p < 0.05). Moreover, total cell number per blastocyst in PZM-3 was clearly higher than in PZM-5 but similar to that in PZM-4. As for SCNT embryos, no significant differences were observed for the cleavage rates or the blastocyst rates among the three groups (p > 0.05). However, total cell number per blastocyst in PZM-3 was notably higher than in PZM-5, but was similar to that in PZM-4. In conclusion, our results suggested that the completely chemically defined medium PZM-4 can be used to efficiently support the early development of porcine PA and SCNT embryos.

Rat 1-cell embryos, recovered from naturally mated females, were cultured in a chemically defined medium (mR1ECM). When examined after 24, 56, 64 and 80h of culture, embryos developed to the 2-cell (100%), 4-cell (93%), 4-cell to 8-cell (97%) and ≥8-cell (95%) stages, respectively. When 0.4 M phosphate (NaH2PO4) was added to the medium after 0, 24, 56 and 64 h of culture, percentages (0–67%) of embryos that developed to the blastocyst stage after 115h of culture were lower than that (86%) in the medium without phosphate. However, addition of phosphate after 80h of culture accelerated blastocyst formation; a significantly higher percentage (94%) of blastocysts was obtained after 110 h of culture in this medium compared with when phosphate was not added (67%). When phosphate was added to the medium after 64h, almost all (97%) 8-cell embryos developed to the blastocyst stage by 100h of culture but development of 4-cell to 7-cell embryos was inhibited (22–63%). Acceleration of blastocyst formation was caused by addition of phosphate rather than by the exchange of the medium. The stimulatory effect of phosphate on embryo development was observed at concentrations of 0.1–1.2mM. The mean numbers of cells (54.5–60.9 cells) in blastocysts examined after 115 h of culture were increased by the addition of 0.4–1.6mM phosphate at 80 h as compared with blastocysts from cultures without phosphate (46.6 cells).