Optimal developmental stage for vitrification of parthenogenetically activated porcine embryos

The objective of this experiment was to determine the optimal developmental stage to vitrify in vitro cultured porcine parthenogenetically activated (PA) embryos. Embryos were vitrified by Cryotop on Day 4, 5 or 6 after oocyte activation (Day 0), and immediately after warming they were either time-lapse monitored for 24 h or analyzed by differential staining. After warming, the embryos had to be cultured for at least 8 h before their survival rates were stabilized. Both the survival rate at 8 h and the hatching rate at 24 h of Day 4 embryos were significant higher than those vitrified on Day 5 or 6 (P < 0.05), no matter if they were morulae or blastocysts. These results demonstrate that porcine PA embryos can survive successfully after vitrification/warming, that the optimal time for vitrification was Day 4 for both morulae and blastocysts, and that 8 h after warming was the time needed to make an early evaluation of porcine PA embryo survival.