Hormonal and physical changes associated with bovine conceptus development

Abstract
Conceptus (placental membranes, fetal fluids and fetus) development was characterized between days 27 and 111 of gestation. Progestagens, estrone, estradiol, estrone sulfate and prostaglandin (PG) F were measured in maternal plasma and allantoic and amniotic fluids. Protein concentrations are described for fetal fluids. The early increase in placental membrane wt from 1.12 g (27 days) to 58.45 g (50 days) was associated with estrogen production presumably of conceptus origin. Estrogens increased significantly in allantoic and amniotic fluids throughout the period studied with estrone being the primary free estrogen, rising from 2 pg/ml (day 33) to 144 ng/ml by 111 days in allantoic fluid. Changes in plasma estrogens of the maternal circulation were not detected until after day 70 at which time estrone concentration was greater than that of estradiol. Fetal fluid concentrations of progestagens, estrone sulfate and PGF were not related to maternal plasma levels and a sequestration of these hormones by the allantois is postulated.