Effect of activation treatments on the in vitro developmental potential of porcine nuclear transfer embryos

In this study the effect of either chemical or physical activating agents was examined as exerted on the in vitro developmental potential of porcine embryos reconstructed by direct microinjection of cumulus cell nuclei into the cytoplasm of enucleated oocytes. In group A reconstituted oocytes were exposed to ionomycin and then to cycloheximide (CHXM), and in group B the oocytes were treated with electrical pulses. The reconstituted oocytes activated electrically showed a higher survival rate than those activated by ionomycin + CHXM (82.2% vs. 71.5%; P less than or equal to 0.01). Cleavage activity and blastocyst formation rates tended to be slightly higher in the chemical activation group than in the electroporation group (61.4% vs. 58.4% and 11.3% vs. 6.2%, respectively), but the differences were not statistically significant (P > 0.05). However, the in vitro developmental rate of nuclear transferred embryos to the morula stage was significantly higher in group A than in group B (57.7% vs. 43.1 %; P less than or equal to 0.05). The blastocyst cell numbers in both experimental groups were comparable (approximately 26.0). In conclusion, the results of the present study indicate that both artificial activation protocols were efficient for the production of porcine nuclear transferred blastocysts to a similar extent.