Urinary Excretion of Estrogen by the Bovine before and after Parturition

Abstract

Total urine was collected from six cows at 8-hr. intervals beginning 3 days before expected parturition and continuing for a maximum of 52 hr. postpartum. Twelve 8-hr. interval samples of urine were collected from each cow (72 samples). Average excretion of 17 β-estradiol, 17 α-estradiol, estrone and estriol was 39±6, 386±23, 226±10 and 24±2 mcg./hr. per 100 kg. of live weight, respectively. Excluding estriol, which was not unequivocally identified, the total excretion of the three identified estrogens was significantly higher during the 8-hr. interval in which parturition occurred than 32, 40 and 48 hr. after calving (P<.01) and 40 hr. before calving (P<.05). The respective percent increases in estrogen excretion from 40 hr. before calving, compared with the 24-hr. average centered around calving, were 18, 29, 28 and 29% for 17 β-estradiol, 17 α-estradiol, estrone and total; similarly, the decreases 48 hr. after calving were 55, 57, 55 and 56%, respectively. Although the quantity of estrogens excreted varied considerably between cows, breeds and intervals, the proportion of each estrogen as a part of the total tended to remain constant between intervals and characteristic for individual cows. Averages were 6.3, 58.7 and 35.0% of the three-estrogen total, respectively, for 17 β-estradiol, 17 α-estradiol and estrone.