Urinary Estrogen Excretion Rates During Pregnancy in the Bovine

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Abstract
Urine was collected from 48 cows from 101 to 285 days of pregnancy, to define urinary excretion rates of estrone, 17[beta]-estradiol, 17[alpha]-estradiol, and an incompletely identified triol, hereafter referred to as estriol. 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 ([mu]g/hr f 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 [plus or minus] 96 [mu]g; 165 to 175 days - 581 [plus or minus] 154 [mu]g; 200 to 212 days - 489 [plus or minus] 136 [mu]g; 226 to 237 days -691 [plus or minus] 104 [mu]g; 250 to 254 days - 1,809 [plus or minus] 580 [mu]g; and 271 to 2and5 days -3,402 [plus or minus] 412 [mu]g. The latter 2 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[beta]-es-tradiol were not significant, but estrone increased significantly (P< 0.01) by 271 to 285 days and 17[alpha]-estradiol increased significantly (P < 0.01) by 250 to 254 days. Excretion rate of estrone tended to be higher or equal to 17[alpha]-estradiol through 237 days, but 17[alpha]-estradiol increased 10-fold thereafter, compared with a 4-fold increase for estrone.