VIABILITY OF CLONED BOVINE EMBRYOS AFTER ONE OR 2 CYCLES OF NUCLEAR TRANSFER AND IN-VITRO CULTURE

We described an exclusively in vitro procedure for cloning and recloni ng bovine embryos. Embryos obtained by IVM/IVF/IVC developed to the mo rula stage were used as blastomere donors in cunjunction with IVM reci pient oocytes. Reconstructed embryos were developed in vitro in cocult ure using bovine oviductal epithelial cells. The resulting morulae wer e used as donors for recloning under the same experimental conditions. No significant difference was observed between cloning and recloning in terms of development (rates of blastocysts: 12.9 versus 14.9%), in the number of nuclei per blastocyst (63.8 versus 49.1), or in pregnanc y rates (35.7 versus 33.3%). The high variability observed between rep licates and the correlation between results in first and second cycle nuclear transfer may suggest an inherant potential of individual donor embryos to support development by cloning.