Effects of Estradiol and Dehydroepiandrosterone on the Reproductive Cycle of the Cow. I. Estrous Cycle Length, Ovulation, Temperature Changes, Vaginal Mucus Flow, Initiation and Maintenance of Pregnancy

Open Access
Publisher Website
Google Scholar
Abstract
Levels of 50, 75, 100, or 150 [mu]g of estradiol per day injected into four cows during each of 15 estrous cycles did not change the length of cycle, the period of time from the onset of estrus to ovulation, the nature or amount of vaginal mucus secretion, or rectal temperature. Daily levels of 200 to 300 [mu]g of estradiol per day decreased the length of the cycle, delayed ovulation, increased mucus secretion and flow elasticity during the middle of the cycle, and increased rectal temperature. Follicles in excess of 20 mm in diameter were present on the ovaries of three cows at varied times when 350 [mu]g of estradiol were injected daily. At a level of 3.5 mg of estradiol daily, no follicular growth above 10 mm in diameter was observed. Estradiol injected at a daily level of 150 [mu]g, which did not completely inhibit normal follicular development and ovulation, interrupted the progress of normal pregnancy when injected from the third to the 16th day following breeding. One cow aborted when injected daily with 250 and 350 [mu]g of estradiol beginning on the 66th day following conception. Pregnancy and parturition were normal in two cows when 250 to 350 [mu]g daily levels of estradiol were initially administered after 100 days of pregnancy. One cow aborted when the same daily levels were injected on the 66th day of pregnancy. Daily injections of 5 or 10 mg of dehydroepiandrosterone (DHA) into each of four cows during eight cycles did not significantly change estrous cycle length, the period of time from onset of estrus to ovulation, the nature of the mucus flow from the vagina, or rectal temperature. DHA at 15 or 20mg per day decreased ovulation time with no significant changes in cycle length. Enlarged follicles were not observed following injections of DHA up to 80 mg per day.

This publication has 16 references indexed in Scilit: