fusion and development of 2-cell bovine embryos to tetraploid blastocyst with different voltages and durations

background: the values of embryonic stem cell and cloning are evident. production of clone from embryonic stem cells can be achieved by introduction of stem cell into a tetraploid blastocyst. tetraploid blastocyst can be produced in vitro by electrofusion of 2-cell embryos. objective: the aim of this study was to assess the effect of different voltages and durations on fusion rate of bovine 2-cell embryos and their subsequent development in vitro. material and methods: the in vitro produced bovine 2-cell embryos were categorized into 3 groups: (1) fused group (fg); 2-cell embryos fused by exposure to different voltages (0.5, 0.75, 1, 1.25 and 1.5 kv/cm) and durations (20, 40, 60, 80 and 100 μs), (2) exposed control group (ecg); 2-cell embryos exposed to different voltages and durations but remained unfused and (3) unexposed control group (ucg); embryos cultured without exposure to any voltage. the embryos from each group were cultured and fusion, cleavage and developmental rates were compared in each group. results: the results show that increased voltage, increases the fusion rate up to 88% for 1.5 kv/cm; however, the rate of cleavage and blastocyst formation decreases significantly to 18% and 10% respectively (p<0.05). increased duration does not significantly increase fusion rate, however, in high voltage, increased duration decreases cleavage rate and blastocyst formation rate. blastocyst formation rate in ucg showed a better development (32%) compared to fg (20%) or ecg (22.5%) (p<0.05). conclusion: it can be concluded that for optimal fusion, cleavage and development, one pulse of 0.75 kv/cm for 60μs should be applied.