Factors Affecting Enucleation Rates of Bovine and Porcine Oocytes After Removal of Cumulus Cells by Vortexing

In vitro matured bovine and porcine oocytes were enucleated by aspiration of the first polar body and adjacent cytoplasm after removing the cumulus cells by vortexing and the factors affecting enucleation rate were investigated. The results indicate that vortexing cumulus-oocyte complexes for long periods in hyperosmotic media moves the first polar body and reduces the enucleation rate. Removal of 20% cytoplasmic volume increased enucleation rate compared with that of 10% and showed no deleterious effect on subsequent developmental capacity of reconstructed bovine embryos. Aging of oocytes could also reduce enucleation efficiency by inducing the migration of the chromatin material to the center of the oocyte. Therefore, we recommend to enucleate newly matured bovine and porcine oocytes by removing the first polar body and adjacent 20% of ooplasm after the removal of cumulus cells by vortexing for a short period using a hypo-osmotic media to achieve a high enucleation rate .