Optimizing Electrical Activation of Porcine Oocytes by Adjusting Pre- and Post-Activation Mannitol Exposure Times

Abstract

Modifying electrical activation conditions have been used to improve in vitro embryo production and development in pigs. However, there is insufficient information about correlations of porcine embryo development with oocyte pre- and post-activation conditions. The purpose of this study was to compare the developmental rates of porcine oocytes subjected to different mannitol exposure times, either pre- or post-electrical activation, and to elucidate the reason for the optimal mannitol exposure time. Mannitol exposure times around activation were adjusted as 0, 1, 2 or 3min. Blastocyst development were checked on day 7. Exposure of oocytes to mannitol for 1 or 2min before electrical activation produced significantly higher blastocyst rates than exposure for 0 or 3min. There was no significant difference in blastocyst rates when activated oocytes were exposed to mannitol for 0, 1, 2 or 3 min after electrical activation. While exposure of oocytes to mannitol for 1min pre- and 3min post-activation showed significantly higher blastocyst development than 0min pre- and 0min post-activation. It also showed higher maintenance of normal oocyte morphology than exposure for 0min pre- and 0min post-activation. In conclusion, exposure of oocytes to mannitol for 1min pre- and 3min post-activation seems to be optimal for producing higher in vitro blastocyst development of porcine parthenogenetic embryos. The higher blastocyst development is correlated with higher maintenance of normal morphology in oocytes exposed to mannitol for 1min pre- and 3min post-activation.