Intrinsic factors affecting apoptosis in bovine in vitro produced embryos.

The main purpose for human assisted reproductive technologies (ART) is clearly to bypass reproductive failures. This purpose is totally different from the aims in animal ART, being genetic improvement and more recently conservation of endangered species. Apoptosis or programmed cell death has been detected before implantation in in vivo as well as in vitro embryos and might contribute to lower developmental competence and embryonic losses of in vitro embryos. In vitro embryo quality is clearly jeopardized by quality of the gametes (oocytes and spermatozoa) and suboptimal culture condition, but there is no consensus on which factor is most important in the incidence of apoptosis during early embryo development. The objective of the present study was to unravel the contribution of both male and female gamete quality to the incidence of apoptosis of bovine embryos produced in vitro. In vivo bull fertility expressed a very low correlation with cleavage rate and blastocyst yield. In contrast, developmental kinetics and oocyte diameter are important markers of embryo developmental potential and embryo quality in terms of the appearance of apoptosis, indicating a significant maternal effect on embryo quality.