SURVIVAL OF THE BOVINE EMBRYO

Selection of most apt individuals for surviving is a biological tendency in evolution. This is repeated in the embryo/fetus during its intrauterine development. During the embryonic period, the new individual is highly vulnerable; the organ systems are established and the ruminant placenta is not completely functional, as in sheep and the cow. These species, in addition to their importance in human nutrition, have been used as research models in human reproduction, given their genetic proximity to man, in spite of the obvious differences in placentation between ruminants and primates.

Embryonic survival is a biological odyssey, which entails participation of an extraordinary number of genetic and epigenetic expressions. As a consequence, multiple molecules interact, some of them known but presumably many more unveiled jet. They are produced, some in the conceptus (the embryo and associated membranes) and the remaining in the uterus, and should function in marvelous and complex synchrony as to succeed in the production of a healthy newborn. The mother should have biological sufficiency as to maintain and accept the conceptus.

In sheep, sows and cows there are huge economic losses due to embryonic mortality (EM; Binelli et al., 2001), even when the animals are under optimal conditions of wellbeing, according to most EM reports.
Around 40% of pregnancies are lost; EM accounts for 70 to 80% of them, and occurs between 8 and 16 days post-insemination (Peters, 1996; Dunne et al., 2000; Humblot, 2001; Diskin et al., 2006; Diskin and Morris, 2008).

In the last years, many research groups have identified participating genes in the expression of key molecules for embryo survival. Some of their results will be exposed in this book, in a general manner. Nevertheless, at present, the complete map of molecular interaction which controls embryonic development and placentation is not available.