Origins and effects of oocyte quality in cattle

Oocyte quality is the resultant of multifactor interactions that should be carefully taken into account either for in vitro embryo production technologies or for studying follicle dynamics. Different approaches may be used to perform an analysis of variables related to oocyte quality which may focus on the ovary, the follicle, the cumulus-oocyte complex and, finally, the oocyte. The information obtained may answer key questions, such as what does the oocyte need to acquire meiotic competence and whether follicle activity can be manipulated to improve the in vitro embryo production efficiency. Although morphological evaluation represents the most common procedure used to discriminate the developmental potential of the oocyte and in spite of a good relationship that has been found between the quality of the oocyte and the atresia grade of the follicle that comprises it, there is not yet a clear correspondence between the visual criteria and the developmental competence of oocytes submitted to in vitro embryo production. New technologies have become available, including emerging 'omics' sciences that, through analysis of the cumulus cells, offer the opportunity, by a non-invasive method, to indirectly predict the developmental potential of the oocyte.