Effect of mSOF and G1.1/G2.2 media on the developmental competence of SCNT-derived bovine embryos

The objective of this study was to compare the effect of two culture media: modified synthetic oviductal fluid (mSOF) and G1.2/G2.2, on the developmental competence of bovine somatic cell-cloned embryos. Cloned embryos were produced by transferring adult skin fibroblasts into enucleated MII oocytes. After activation, the reconstructed embryos were randomly allotted to either mSOF or G1.2/G2.2 for culture (the embryos were transferred from G1.2 to G2.2 on days 3 of culture). The development competence of cloned embryos in these two culture systems was compared in terms of cleavage rate, blastocyst formation rate and apoptosis cell number in day 7 blastocyts. To investigate the in vivo developmental competence of cloned embryos in the two culture systems, a total of 87 and 104 blastocysts derived from mSOF and G1.2/G2.2 medium groups were transferred individually to recipient Angus cows, respectively. No differences were observed in terms of cleavage rate, day 7 blastocyst rate and blastocyst cell number between these two culture systems. However, the day 6 blastocyst formation rate was significantly higher in G1.2/G2.2 than that in mSOF. In addition, blastocysts cultured in mSOF have a higher percentage of apoptotic blastomeres compared to those in G1.2/G2.2 (8.5 ± 1.2 vs 16.8 ± 1.5, p<0.05). Although difference in pregnancy rate was not observed 40 days after embryo transfer, significantly higher pregnancy rate was observed in G1.2/G2.2 group after 90 days of embryo transfer (12.4% vs 37.5%, p<0.05). Moreover, calving rate was significantly improved in G1.2/G2.2 group compared to mSOF group (27.9% vs 6.7%, p<0.05). In conclusion, our results indicate that G1.2/G2.2 can improve developmental competence of bovine SCNT embryos both in vitro and in vivo, which is more suitable for culture of bovine SCNT embryos than mSOF medium.