In somatic cell nuclear transfer in mammals, to clone a piglet is still a big challenge. Although many factors could contribute to the low success rate, such as quality of donor and recipient cells, types of donor cell including sources of animal breeds and tissues, number of passages and culture conditions, timing of cell cycle, procedures of nuclear transfer, techniques and embryos transfer, one of the factors is believed to be poor oocyte activation, especially in pig nuclear transfer. Therefore studies presented in this thesis aimed at the establishment of an in vitro culture system for pig oocyte maturation and embryo culture, based on this system an electrical activation protocol for pig oocytes was optimized and also tested by monitoring in vivo development of activated pig oocytes. Finally, the protocol was used for activating pig embryos reconstructed by transfer of somatic cells into enucleated ovulated oocytes and for production of pig parthenotes to maintain pregnancies of cloned pig embryos, which resulted in the birth of a cloned male piglet. The thesis comprises a total of 6 chapters. In addition to the review of literature (Chapter 1), general materials and methods (Chapter 2) and general discussion (Chapter 6), in Chapter 3 and 4, the studies focused on optimizing electrical parameters on pig oocyte activation and investigating the effects of activation conditions including temperature, activation medium, and concentrations of Ca²⁺ and Mg²⁺ in activation medium and diploidization of activated oocytes. These experiments were carried out in vitro, whereas experiments in Chapter 5 were conducted in vivo to assess the in vivo developmental competence of in vitro matured (IVM) pig oocytes activated by the improved activation protocol.