Elsevier

Theriogenology

Volume 85, Issue 2, 15 January 2016, Pages 330-334
Theriogenology

Research article
Effect of copulation on estrus duration and ovulation time in goats

https://doi.org/10.1016/j.theriogenology.2015.09.021Get rights and content

Abstract

The objective of the present study was to evaluate the effect of copulation on estrus duration and ovulation in goats. During the fall season, 14 multiparous Boer does were estrous synchronized with controlled internal drug release (300 mg), maintained in the vagina for 7 days, and received 50 μg of intramuscular GnRH device insertion and 5 mg of natural intramuscular PGF2α at device removal. The does were randomly divided into two equal groups: a treatment group (TRE; n = 7) and a control group (CON; n = 7). The TRE group received two copulas by fertile bucks within the first 4 hours of estrus onset, and the CON group received only mounts by the same males equipped with canvas aprons. Estrus detection was performed every 12 hours after controlled internal drug release removal within the first 24 hours and then every 4 hours for 5 days. Estrus was defined when a doe accepted mounting by the bucks equipped with canvas aprons. Each doe in estrus got the first transrectal ultrasonography at 24 hours after estrus onset and then every 4 hours until all the preovulatory follicles ovulated. Estrus onset for the TRE and CON groups was 40.3 ± 17.4 (mean ± standard deviation) and 43.3 ± 12.2 hours (P = 0.72), respectively. Estrus duration for the same groups was 28.6 ± 5.4 and 36.7 ± 5.3 hours (P = 0.02), respectively. The mean ovulation time for the TRE and CON groups was 31.4 ± 2.2 and 35.7 ± 3.7 hours (P = 0.04), respectively. The proportion of ovulations that occurred after the end of estrus in the TRE group was higher than in the CON group (86% vs. 33%, respectively; P = 0.05). The number of ovulations for the TRE group was 2.1 ± 0.7; for the CON group, there were 2.2 ± 0.5 ovulations (P = 0.92). It was concluded that copulation by a buck at the beginning of estrus reduced estrus duration and hastened the ovulation time in Boer goats.

Introduction

Caprine estrus length exhibits great variations [1], [2], [3], [4]. Estrus duration is essential to artificial insemination (AI) technology [5], [6]. It has been traditionally recommended that goats be inseminated 12 hours after the onset of estrus and inseminated again the following day if they are still in estrus [6] or immediately after estrus detection and 12 hours later [7]. Previous studies have shown decreased estrus duration between 9.3 and 19.2 hours (26%–44% reduction compared with the control group) after copulations during the first 12 hours of estrus [4], [8], [9], [10], [11], [12]. This effect was independent of the number of copulas at the same estrus [8]. It was also found that the decline in estrus duration was due to the mechanical effect of the penis-like device against the vaginal fornix [9]. When the mechanical effect of the penis was eliminated by local and regional anesthesia of vagina and cervix of the does, after which the male was permitted to copulate the females, no reduction in estrus duration was observed [10]. It was also noticed that the accessory sexual fluid did not show any effect on estrus duration [10]. Interestingly, when a copula was permitted by a vasectomized teaser before the AI, an increase in fertility rate was noticed compared with a control group of noncopulated females that were inseminated with the same semen [12]. However, no differences between control (CON) and treatment (TRE) groups either in the number of ovulations or ovulation times were detected when assessed at 8-hour intervals by laparoscopy [11]. Because of the 8-hour interval used among examinations, the likelihood of overlooking some real differences in ovulation times between groups cannot be ruled out. Therefore, if the periods between assessments are reduced, a more accurate estimation of plausible differences between groups in the ovulation time could be recognized.

The objective of the present experiment was to evaluate the effect of copulation on estrus duration and ovulation in Boer goats.

Section snippets

Animals and experimental design

All procedures used in this experiment were in compliance with the Guide for the Care and Use of Agriculture Animals in Research and Teaching and were approved by the Texas A&M University Institutional Animal Care and Use Committee. The Teaching and Research Goat Herd from the Department of Large Animal Clinical Sciences was used. A controlled randomized design with two groups, CON (n = 7) and TRE (n = 7), was performed. The TRE group was permitted to receive two copulas within the first

Results

A summary of all the results from this investigation can be seen in Table 1. All the females in this study presented estrus after CIDR removal but one doe from the CON group. The estrus onset for the TRE and CON groups was 40.3 ± 17.4 and 43.3 ± 12.2 hours (P = 0.72), respectively. The estrus duration for the same groups was 28.6 ± 5.4 and 36.7 ± 5.3 hours (P = 0.02), respectively. All the females in estrus ovulated (n = 13). The first ovulation was earlier for the TRE group compared with the

Discussion

In the present investigation, the time of estrus onset between groups was similar to a previous report that used CIDR [17]. This interval was different from other progestogens such as fluorgestone acetate or medroxyprogesterone acetate [17], [18]. The probable reasons for this difference could be due to the different absorption and metabolization of these progestogens as suggested for sheep and goats [18], [19].

Copulation provides the female with important genital stimulation. It is necessary

Acknowledgments

This research was supported by a competitive grant from the Department of Large Animal Clinical Sciences (RGS 13-18) of the College of Veterinary Medicine and Biomedical Sciences of Texas A&M University (Project: Endocrine responses to copulation in goats). The authors also thank the Department of Large Animal Clinical Sciences personnel responsible for the support and care of animals of the Teaching and Research Goat Herd. They also thank the Veterinary Medical Research Park of Texas A&M

References (36)

Cited by (7)

  • Effect of copulation on estrus duration, LH response, and ovulation in Boer goats

    2018, Theriogenology
    Citation Excerpt :

    However, based on the findings of a previous study, this factor was not considered, because no differences, when examined by laparoscopy at 8-hour intervals, either in ovulation times or number of ovulations by effect of copulation, were detected [5]. Nevertheless, a recent investigation noticed that ovulation times were hastened by effect of copulation when assessed by transrectal ultrasonography at 4-hour intervals [6]. Therefore, this last outcome encouraged revisiting the possibility that copulation by the teasers could have been involved in the increase of fertility.

  • Vulvar thermal pattern following synchronization of estrus is linked to fertility after timed artificial insemination in goat

    2017, Theriogenology
    Citation Excerpt :

    In the present work, the differences in the vulvar and perivulvar thermal patterns between pregnant and not pregnant goat treated with the same TAI protocol were evaluated and determined. Pregnancy rate obtained during the TAI protocol was not different from other studies reported for goat species [1–4,25]. A significant VST average decrement was evident only in pregnant females on the artificial insemination time.

  • Continuous presence of male on estrus onset, estrus duration, and ovulation in estrus-synchronized Boer goats

    2016, Theriogenology
    Citation Excerpt :

    A novel finding of the present investigation was that the permanent presence of the male without copulation reduced the estrus duration compared with the group of females in intermittent presence with the male without copulation. This confirms the suspected influence from a previous study that the continual presence of male could decrease estrus duration [13]. Estrus duration in both studies was similar.

View all citing articles on Scopus

Deceased.

View full text