The effective culture method of zona-free rabbit 1-, 2- and 4-cell embryos

The effect of modified incubation systems on the development capacity of the zona-free rabbit embryos was examined. Embryos at 1-, 2- and 4-cell stages were used. The removal of the zona pellucida was accomplished by the enzymic-mechanical technique. Denuded rabbit embryos were cultured using 3 incubation systems. In the first and the second system the embryos were cultured in microdrops. The difference between these first 2 systems concerned the volume of the microdrops and the kind of paraffin oil used. In the first system the embryos were cultured in 5mul microdrops covered with light or heavy paraffin oil; in the second system embryos were cultured in 40-mul microdrops under light paraffin oil. The third traditional system involved the incubation of embryos in glass capillaries into separated columns of medium. The percentage of blastocysts obtained from 1-cell embryos cultured in the first incubation system was 6.1% with heavy paraffin oil as the covering layer and 29.0% with light paraffin oil. In the second and third incubation systems blastocyst yield was 30.8 and 59.6%, respectively. The percentage of blastocysts obtained from 2-cell and 4-cell stage embryos with heavy paraffin oil was 18.7 and 25.0%, respectively; with light paraffin oil these figures were 40.0 and 50.0%, respectively. In the second incubation system these figures were 49.3 and 72.3%; and in the third incubation system they were 72.9 and 78.3%, respectively. The results of the experiment showed that culture into glass capillaries is undoubtedly an effecient method of culturing of the zona-free rabbit embryos.