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Urinary Excretion of Estrogenic Compounds During Estrus and Gestation by the Bovine as Determined by Three Assay Methods

Department of Animal Science, Montana Agricultural Experiment Station, Bozeman

ABSTRACT

Aliquots of 24-hr urine collections from cows during estrus and at the 50th, 100th, 200th, and 275th days of gestation were extracted and assayed for the estrogenic content by the Kober color reaction, fluorometrically, and with bioassay. The bioassay procedure gave results for estradiol-17 that averaged 1.19 times higher than those obtained by the Kober color reaction and 1.74 times higher than the fluorometric results. However, in measuring estradiol-17ß, the bioassay results were 0.7 times greater than the Kober results and 0.54 times greater than, the fluorometric results. The greatest differences between the methods were revealed in measuring urinary estrone, in that the bioassay results averaged only 0.21 times greater than the Kober results and 0.42 times higher than the fluorometric results.

Excretion of the three estrogens was lowest at 50 days, but after 100 days of gestation an increase in urinary estrogenic excretion occurred and it was at an accelerated rate during the last stages of pregnancy. The most pronounced increase was in the excretion of estradiol-17, although estrone excretion was also considerably higher during the latter part of gestation. The urinary excretion of estradiol-17ß increased at a much slower rate than did that of two other estrogens.