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Urinary Estrogen Excretion Rates During Pregnancy in the Bovine¹

Department of Animal Sciences, Purdue University, Lafayette, Indiana, and Washington State University, Pullman

ABSTRACT

Urine was collected from 48 cows from 101 to 285 days of pregnancy, to define urinary excretion rates of estrone, 17 ß-estradiol, 17 -estradiol, and an incompletely identified triol, hereafter referred to as estriol. Enzyme hydrolysis was used as the first extraction step to minimize destruction of 17 -estradiol. The estrogens were separated and purified by paper partition chromatography and measured fluorimetrically. Breed, age, and live weight of the cow were not significantly related to excretion rate when the latter was adjusted to a 500-kg basis (µg/hr ÷ live weight x 500 kg). Average total estrogen excretion ± one standard error per hour per 500 kg during pregnancy was as follows: 101 to 123 days—300 ± 96 µg; 165 to 175 days—581 ± 154 µg; 200 to 212 days—489 ± 136 µg; 226 to 237 days—691 ± 104 µg; 250 to 254 days—1,809 ± 580 µg; and 271 to 285 days—3,402 ± 412 µg. The latter two means were significantly higher than means of each of the other periods. Estriol excretion was highest during 250 to 254 days (P < 0.01, except for 226 to 237 days). Changes in 17 ß-estradiol were not significant, but estrone increased significantly (P < 0.01) by 271 to 285 days and 17 -estradiol increased significantly (P < 0.01) by 250 to 254 days. Excretion rate of estrone tended to be higher or equal to 17 -estradiol through 237 days, but 17 -estradiol increased tenfold thereafter, compared with a fourfold increase for estrone.

¹ Journal Paper no. 3115, Purdue University Agricultural Experiment Station, 47907, Projects 1306 (Indiana) and 1585 (Washington). A contribution from Western Regional Research, Project W-49.

² Purdue University.

³ Present address: Merck Institute for Therapeutic Research, Rahway, New Jersey.

⁴ Washington State University.