Exposure to Estrogen Mimicking the Level of Late Pregnancy Suppresses Estrus Subsequently Induced by Estrogen at the Level of the Follicular Phase in Ovariectomized Shiba Goats

Abstract

A high-estrogen environment during late pregnancy is suspected to cause postpartum silent ovulation, and progesterone (P4) is suggested to recover estrus. However, few attempts have been undertaken to elucidate the influence of these steroids on estrus by analyzing hormonal profiles. We investigated estrus and luteinizing hormone (LH) surges in ovariectomized goats (n=6) assigned to three treatments in a cross-over design. In groups 1 and 2, 200 µg/kg body weight/day estradiol benzoate (Dose-200 E2B) was administered for 14 days concurrent with P4 for 11 days, while in the control, saline solution and P4 were administered likewise. Ten days after the final administration of Dose-200 E2B, group 2 was treated with P4 for 8 days, and all groups were treated with 2 µg/kg body weight E2B (Dose-2 E2B) 20 days after the final administration of Dose-200 E2B (or saline solution). The proportion of cases expressing estrus after the administration of Dose-2 E2B was smaller (P<0.01) in group 1 than in the control (1/6, 3/6 and 6/6; groups 1 and 2 and the control, respectively). The proportions of cases generating LH surges did not differ (P>0.1) among the groups (5/6, 5/6 and 6/6; groups 1 and 2 and the control, respectively), but the peak concentrations in groups 1 and 2 (26.2 ± 14.7 and 11.3 ± 6.7 ng/ml) were lower (P<0.01) than those in the control (67.8 ± 19.4 ng/ml). These results demonstrated that elevation of plasma estrogen mimicking late pregnancy inhibits the subsequent estrus induced by estrogen simulating the follicular phase.

Reproductive activity of dairy cattle in the postpartum anestrus period

“…Hormonal strategies to induce this generally include the use of progestogens, estradiol and GnRH. The progestogens are used to sensitize the hypothalamus to the effect of the estradiol following calving, such that the female can exhibit the behavior of estrus (Figure 2; Nagai et al, 2013).…”

Effect of intermittent administration of neurokinin 3 receptor agonist on luteinizing hormone secretion, estrus, and ovulation in feed-restricted goats

“…Observation of estrus and blood sampling were commenced at 6-h intervals from 24 to 96 h after the start of treatment. Estrus and estrous signs were checked just before the blood sampling, according to a method described previously (Nagai et al, 2013). Estrus was defined as when a female goat stood to be mounted by a male goat.…”