Reproductive Steroids in the Bovine. IV. Urinary Estrogen Excretion Rates from 0 to 9 Days after Breeding in Fertile and Nonfertile Cows

Abstract

Urine samples were collected from 23 lactating dairy cows at breeding and daily for nine days thereafter. The objective was to determine if cows failing to conceive exhibited an altered urinary estrogen excretion pattern from that of cows conceiving. The cows were divided into four groups based on days to return to estrus, namely Group 1—less than 19 days; Group 2–19 to 24 days; Group 3–34 to 49 days; Group 4—pregnant. The number of cows in each group was 6, 7, 5 and 5, respectively. When compared to the highest and lowest daily rates observed for individual pregnant cows on the same day, total estrogen excretion rates by Groups 1, 2 and 3, respectively, were higher for 50, 57 and 20% of the comparisons on day 1, for 50, 57 and 60% of the comparisons on day 5 and for 67, 57 and 20% of the comparisons on day 9. Groups 1 and 2 excreted significantly (P<.10 to P<.05) less estradiol-17a on the day of breeding and excreted more estradiol-17a on day 9 than did Group 4. It is postulated that relatively large deviations in metabolism of estrogen in infertile cows as compared to pregnant cows may cause asynchronization between tubal transport of ova and progestational changes required in the uterine mucosa to support zygotes. Copyright © 1971. American Society of Animal Science. Copyright 1971 by American Society of Animal Science.