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Estrogen Content of Colostrum and Milk of Dairy Cattle^{1, 2,}

Department of Dairy Husbandry, University of Missouri, Columbia

ABSTRACT

A study of the permeability of the secreting mammary gland epithelial cell to circulating blood estrogens is reported. Milks were dried and fed to ovariectomized mice for ten days. The increase in uterine weight of these mice was compared to controls and to those fed graded amounts of diethylstilbestrol added to dried whole milk, to estimate the estrogen in milk. Milks from 11 nonpregnant cows, producing from 26.9 to 66.8 lb. per day, were assayed. The average uterine weight of the group was 10.48 mg., and uterine weight/% of body weight was 0.05. The milk of nonpregnant cows either is free of estrogen or it contains amounts which can not be detected by the assay method. Milks from 32 cows, pregnant from 27 to 268 days, were assayed. The milk of ten cows, pregnant from 27 to 97 days, averaged mouse uterine weights of 11.35 mg., with an average uterine weight/% body weight of 0.06. Milk of 11 cows, from 104 to 193 days pregnant, averaged uterine weights of 13.71 mg., with an average uterine weight/% body weight of 0.07. Milk from 11 cows, from 200 to 268 days pregnant, averaged uterine weights of 16.45 mg., with an average uterine weight/% body weight of 0.09. These data indicate that the normal lactating cells are only slightly permeable to the normal circulating estrogen of the cow's blood, even in late pregnancy, when estrogen secretion is high and secretion of milk is low. Commercial market milk samples were obtained monthly for 18 mo. The average uterine weight of mice was 11.32 mg. and uterine weight/% body weight was 0.06. Samples of colostrum from six normal cows and from three cows experimentally induced to lactate showed low uterine weight increases. These observations are significant, because the secretion of estrogen in late pregnancy is at a maximum and the rate of colostrum (milk) secretion is minimal. Seven nonpregnant cows, producing from 5.4 to 26.8 lb. per day, were fed diethylstilbestrol at from 10 to 20 mg. per day per 1,000 lb. live weight, for 2 wk. or more. Nine samples from cows fed 10 mg/day showed average uterine weight of 12.07 mg. and an average uterine weight/% body weight of 0.07. These data indicate that the secreting mammary gland epithelial cell either is nonpermeable or is only slightly permeable, to circulating natural estrogenic hormones or to synthetic estrogens (diethylstilbestrol) when fed at levels of from 10 to 20 mg/day/1,000 lb. body weight.

¹ Contribution from the Missouri Agr. Expt. Sta., Journal Series No. 1809. Approved by the Director.

² This investigation was supported in part by a grant from the American Cancer Society.

³ With the technical assistance of Mary E. Powell.

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