PLASMA LEVELS OF ESTRONE SULFATE, ESTRONE AND ESTRADIOL-17β IN THE COW AROUND PARTURITION

Abstract

Estrone sulfate, estrone, and estradiol-17β have been assayed in blood plasma taken from the mammary vein of five pregnant cows before and after parturition. While there were considerable individual variations, the mean plasma levels of estrone sulfate (13.4 ng/ml), estrone (1 ng/ml) and estradiol-17β (1 ng/ml) remained fairly constant over the period of blood collection prior to parturition (−88 h to −2 h). The levels of all three estrogens dropped rapidly within 8 h postpartum. It is concluded that estrone sulfate, rather than estrone, is the predominant plasma estrogen in late pregnancy in the cow.