PRESENCE OF MITOTIC CELLS - A PARAMETER OF EMBRYO QUALITY

The aim of this study was to identify objective parameters for measuri ng embryo quality instead of those based on morphological appearance. We have investigated the relationship between embryo quality as assess ed by morphological appearance and the number of blastomeres in bovine embryos at 5-7 days as well as the relation between embryo quality an d presence of mitotic and pycnotic nuclei. Superovulated cows were sla ughtered from 5 to 7 days after ovulation and embryos were flushed fro m the excised uteri. They were fixed in acetic acid-ethanol, and stain ed with orcein, following qualification according to their morphologic al appearance by microscopy. Blastomere numbers were determined for ea ch day and quality. Some of the Day- embryos were classified according to the presence of mitotic and/or pycnotic cells. The number of blast omeres per embryo increased with increasing quality and with age excep t for poor embryos, where the number of blastomeres remained low. Clas sification of the Day-6 embryos according to the status of their cells , showed that 72% of the excellent and good embryos were categorized a s having mitotic cells. Of the embryos that were classified as fair or poor, 53.5% had no visible mitotic activity. Mitotic activity is indi cative of embryo quality. It is correlated with high numbers of blasto meres and might be responsible for embryo viability.