EMBRYONIC DEVELOPMENT AND HORMONAL ANTILUTEOLYTIC STRATEGIES FOR EMBRYO TRANSFER PROGRAMS IN CATTLE

During embryonic development multiple interactions are stablished between hormones, growth factors (GF) and different type of molecules, generating a series of signals that unchain the maternal recognition of pregnancy (MRP) between days 15 and 17. During this “critical period”, the endometrium liberates the hormone prostaglandin F2α (PGF2α) to cause luteolysis of the corpus luteum (CL), which synthesizes progesterone (P4), which, in turn, favors the production of endometrial secretions necessary for the successful establishment and development of the embryo and maintenance of pregnancy. The developing embryo generates antiluteolitic signals that block the production of PGF2α, suggesting that the maintenance of pregnancy is dependent upon (among other factors) the effectiveness of this blocking. The blocking is generated by the action of Interferon tau (IFN-τ), produced in mononuclear cells of the embryonic trophoblast. This blocking guarantees the integrity of the CL and thereby the normal production of P4. The forgoing suggests that hormonally supported strategic manipulation improves the effective blocking of luteolytic agents that have their greatest activity during the “critical period”. This improves the survival rate in embryonic transplant programs by creating a uterine environment adequate for the establishment and normal development of the embryo. Mechanisms of hormonal support have been proposed that would results in blocking of the production of uterine PGF2α during the critical period between days 15 and 17 of the estrus cycle.