Vol. 7, Issue 2, Part A (2025)

Reproduction in ruminants is a highly complex and variable biological process among species. This is apparent when one reflects on the natural evolution of multiple strategies involving the hypothalamic-pituitary-gonadal-uterine axis employed to achieve pregnancy recognition signaling, implantation and placentation, fetal growth and development and parturition for successful outcomes of pregnancy. The maternal system plays a coordinating role in IFN-τ production by controlling the timing and magnitude of IFN-τ output by the conceptus. The peak production of IFN-τ occurs before uterine attachment but at a time when luteal regression must be blocked to maintain the pregnancy. IFN-τ suppresses the normal pattern of pulsatile release of uterine prostaglandin F2α (PGF2α) leading to luteolysis at the end of the oestrous cycle. Generation of luteolytic episodes of PGF2α secretion requires luteal secretion of oxytocin and the interaction of circulating oxytocin with its receptor, which is located principally on endometrial epithelial cells. IFN-τ modulates uterine PGF2α release by inhibiting endometrial oxytocin receptor expression. Recombinant IFNT administration was reported to inhibit luteal regression and extend the luteal phase for only a few days. Comparing the efficacy of using an intrauterine device carrying interferon tau with the administration of exogenous progesterone in cows might be beneficial, especially with regard to pregnancy success rates in cattle. In systems that use artificial insemination and estrus synchronization, this contrast may be particularly pertinent.