How to select ‘the’ embryo for transfer: novel insights from advanced genetic analysis of bovine and equine embryos

Korte beschrijving

Early embryo development involves a large number of sequentially coordinated and complex events, to which each parent contributes. The complexity of early embryonic development is reflected in cattle, horses and humans by the fact that most of early life seems to die rather prenatally than postnatally. Indeed, only about 30-44.5, 35, and 30% of in vivo-conceived bovine, equine and human gestations are respectively successful, resulting in liveborn offspring. Fertility can be increased by the application of assisted reproductive technologies (ART), allowing for production of more embryos that can be transferred to the uterus and additionally, be selected or ranked upfront according to their quality. Yet, with the help of ART, reproductive efficiency drops even further; an estimated rate of only 9.5, 13 and 12.5% of in vitro-fertilized bovine, equine and human oocytesresultsin liveborn offspring, respectively. Increased early embryonic mortality and pregnancy loss following ART is attributed to the exposure of the gametes and embryos to a suboptimal unnatural environment for a shorter or a longer time during the crucial and vulnerable period of gametogenesis and early embryonic development, which invariably imposes stresses upon them.