Abstract: Factors affecting the efficiency of nuclear transfer (NT) in rabbits were examined in the present study. When 100 V·mm-1 of pulse strength and 15μs of pulse duration were employed, 3 and 4 electronic pulses resulted in significantly more cytoplasts fused with donor cells compared with 2 electronic pulses (P<0.05), but no significant difference was found in the cleavage rate of reconstructed embryos among the three groups (P>0.05). When the duration and number of electronic pulse were fixed at 15μs and 3 times, increase of pulse intensity from 100 V·mm-1 to 150 V·mm-1 and 200 V·mm-1 resulted in a significantly decrease in the cleavage rate of reconstructed embryos (P<0.05), although the fusion rate did not significantly differ among the three groups (P>0.05). Significantly more reconstructed embryos cleaved and developed to blastocysts when they were derived from donor embryos at the 8-16-cell stage, in comparison with the reconstructed embryos derived from donor embryos at the compact morulae stage (P<0.05), although the fusion rate was similar (P>0.05). Activation of cytoplasts prior to fusion increased the cleavage rate (P<0.05) and blastocyst development (P<0.05) of reconstructed embryos, but decreased the fusion rate (P<0.05) compared with cytoplasts activated post fusion. More reconstructed embryos developed to blastocysts when they were cultured in TCM＋3%OCS at the first 48 h and then cultured in TCM199＋10% FCS, in comparison with the reconstructed embryos cultured in either TCM199＋10%FCS or TCM199＋3%OCS (P<0.05). When 22 NT embryos were transferred into the oviducts of one recipient rabbit, one rabbit was delivered to birth. In conclusion, either electrofusion parameter or developmental stage of donor embryos have a significant effect on the efficiency of NT, NT embryos require different concentration of serum at their different development stages.

Key words: Rabbit, Nuclear transfer, Embryo