Abstract: The purposes of the present study were to evaluate cold storage of maturation medium on nuclear maturation, subsequent development in vitro of these oocytes after parthenogenetic activation, and to determine an optimal protocol for porcine oocyte activation. The results were as following: ①Death rate of oocytes after electrical stimulation was significantly higher in group of 1.4 kv/cm,100μs,1DC than that in group of 2.0 kv/cm,30μs,1DC or in group of 2.0 kv/cm,60μs,1DC. The rates of cleavage and blastocyst formation，however， were similar among these goups. ②When chemicals: inomycin and 6-DMAP were used as activation agents, the cleavage and blastocyst rates were both poorer than when electrical stimulation was used. ③After 6 replicates, we found that the rates of nuclear maturation, cleavage, blastocyst formation were all similar between oocytes matured in culture media prepared from cold storage in -20℃ and 4℃. In conclusion, optimal activation protocol was determined and cold storage of maturation medium under -20℃ is feasible without compromising developmental competence of porcine oocytes.

Key words: pig; oocyte; parthenogenetic activation; in vitro maturation; cold storage