Estrogens in the Bovine-A Review

Abstract

This review was made to indicate progress in describing the role of estrogenic substances in bovine reproduction. Chemical methods appear adequate for measuring estrogen in urine and most tissues, but more sensitive methods, such as double isotope derivative assay, need to be thoroughly studied and tested before reliable estimates can be made in peripheral blood. In vitro studies show that estrogens can arise in the bovine adrenal, ovary, and placenta from (a) acetate, (b) cholesterol, (c) progesterone, or (d) neutral C19- and C18- steroids. Estrone, 17 β-estradiol, and 17 α-estradiol have been unequivocally identified in the cow. Others have been suggested, but none appears to be satisfactorily identified. Estrone has been identified in bovine adrenals, bile, fetal cotyledons, feces, and urine. Only 17 β-estradiol has been tentatively identified in whole ovaries and follicular fluid. Urine and fetal cotyledons contain 17 α-estradiol, estrone, and 17 β-estradiol. Estrogenic biological activity has been detected in peripheral blood from anestrus, cycling, and pregnant cows, in amniotic and allantoic fluid, colostrum, milk, ovaries, follicular fluid, corpora lutea, placenta, feces, and urine. The urinary excretion of estrogens increases rather dramatically during the terminal stages of pregnancy, reaching a peak immediately before parturition, followed by a steady decline post-partum. Quantitative estimates presently available are extremely variable. Though qualitative and general interpretations can be made, conclusive quantitative description is currently impossible. © 1965, American Dairy Science Association. All rights reserved.