[Total estrogen concentrations in the blood plasma of calves during the first six days of life].

From 47 mature calves ten blood samples were taken during the first six days of life for determination of total estrogen concentrations. Immediately postnatal concentration of total estrogens in blood plasma was high (1093.2 +/- 452.5 pg/ml blood plasma). Total estrogen values increased towards the sixth hour of life (1789.0 +/- 892.2 pg/ml blood plasma), which is thought to be caused by reabsorption of estrogens released from intracorporeal reservoirs. Towards the 48th hour of life total estrogen values decreased. This decrease indicates a progressive depletion of the reservoirs and also metabolisation and elimination of estrogens by the organism. The fact that total estrogens were nearly unchanged from the 4th day of life onwards reveals the approximative completed elimination of estrogens. At no time significant differences of total estrogen concentrations in blood plasma were found between female and male newborn calves.