Estrogen Content of Colostrum and Milk of Dairy Cattle

Abstract

A study of the permeability of the secreting mammary gland epithelial cell to circulating blood estrogens is reported. Samples of milk were dried and fed to ovariectomized mice for a 10 day period. The increase in uterine weight of these mice was compared to control animals and those fed graded amounts of diethylstilbestrol added to dried whole milk, in order to estimate the amount of estrogen in the milk. Milk samples from 11 nonpregnant cows and from 32 cows pregnant from 27 to 268 days, indicated that normal lactating cells are only very slightly permeable to normal circulating estrogen of the cows blood even in late pregnancy when estrogen secretion rate is high and milk secretion low. Samples of colostrum from 9 cows showed only low increases in uterine weight. Milk from lactating cows fed diethylstilbestrol at levels ranging from 10 to 20 mg/day/1000 lbs. live weight for 2 weeks or more indicated that synthetic estrogen, as well, is either non-permeable or only slightly permeable.