Embryonic mortality in cattle from the embryo's perspective

Abstract

For the embryo to successfully complete development it must be capable of executing its developmental program within a microenvironment largely established by the mother. Mortality results either because of intrinsic defects within the embryo, an inadequate maternal environment, asynchrony between embryo and mother, or failure of the mother to respond appropriately to embryonic signals. To some extent, the embryo’s fate is dictated by events before fertilization: embryos formed from incompetent oocytes have a low probability of successful development. For example, embryos have reduced developmental competence when formed from oocytes from persistent ovarian follicles or from cows during the summer in Florida. Chromosomal abnormalities, caused by incompetent gametes or other causes, and homozygous recessive genes, exacerbated by inbreeding, represent additional types of intrinsic errors responsible for embryonic loss. Alterations in the maternal environment can cause embryonic mortality, as has been shown for heat stress and feeding diets high