Viability of cloned bovine embryos after one or two cycles of nuclear transfer and in vitro culture

We described an exclusively in vitro procedure for cloning and
recloning bovine embryos. Embryos obtained by IVM/IVF/IVC developed to the
morula stage were used as blastomere donors in cunjunction with IVM recipient
oocytes. Reconstructed embryos were developed in vitro in co-culture using bovine
oviductal epithelial cells. The resulting morulae were 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
pregnancy rates (35.7 versus 33.3%). The high variability observed between replicates
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