Centro de Investigación en Reproducción Caprina (CIRCA), Programa de Posgrado en Ciencias Agrarias, Universidad Autónoma Agraria Antonio Narro, Torreón, Coahuila, Mexico.
Physiologie de la Reproduction et des Comportements, CNRS, IFCE, INRA, Université de Tours, Agreenium 37380, Nouzilly, France.
Domest Anim Endocrinol. 2019 Oct;69:68-74. doi: 10.1016/j.domaniend.2019.04.006. Epub 2019 Apr 30.
In male goats, being in permanent visual contact with females in estrus does not prevent seasonal variation in certain endocrine hormone levels and sexual activities. In this study, we tested whether continuous and full contact with females in estrus prevented seasonal endocrinological variation in bucks. In 1 experiment (Exp. 1), we verified that the sudden introduction of goats in estrus increased the plasma concentrations of androgen in bucks during the nonbreeding season under our experimental conditions. In another experiment (Exp. 2), we tested the ability of estrous goats to prevent seasonal inhibition of LH and androgen secretions in bucks kept in permanent and full contact with them. In Exp. 1, 3 groups of bucks (n = 5 in each group) were isolated from females from the months of July to January. On January 27, one group continued being isolated from females; a second group was exposed to ovariectomized, untreated goats; and a third group was exposed to ovariectomized goats with induced estrus. Plasma androgen concentrations were determined every 2 h from 8 h before to 8 h after the introduction of females. The introduction of estrus-induced goats significantly increased androgen concentrations, which were higher than in the isolated bucks, as well as in those exposed to untreated goats (P < 0.05). In Exp. 2 (n = 5 per group), one group of bucks was isolated from females from October to July, whereas two other groups remained in contact with ovariectomized goats, either untreated or regularly induced to estrus. In the three groups of bucks, plasma concentrations of LH were determined once during the months of October, February, March, and June, whereas androgen concentrations were determined weekly from October to July. The mean plasma LH and androgen concentrations were low and did not differ among the groups of bucks during the normal seasonal period of sexual inactivity (P > 0.05). We conclude that full contact and sexual interactions with estrus-induced goats failed to stop the seasonality of LH and androgen plasma concentrations of bucks, although bucks could respond to the introduction of females by acute increases in plasma LH and androgen.
在雄性山羊中，与发情雌性动物保持永久的视觉接触并不能防止某些内分泌激素水平和性活动的季节性变化。在这项研究中，我们测试了与发情雌性动物的持续和完全接触是否可以防止公山羊季节性的内分泌变化。在一项实验（实验 1）中，我们验证了在我们的实验条件下，突然引入发情的山羊会增加非繁殖季节公山羊的血浆雄激素浓度。在另一项实验（实验 2）中，我们测试了发情雌性动物是否能够防止与它们保持永久和完全接触的公山羊的 LH 和雄激素分泌受到季节性抑制。在实验 1 中，将 3 组公山羊（每组 5 只）从 7 月到 1 月与雌性隔离。1 月 27 日，一组继续与雌性隔离；第二组接触未处理的去卵巢山羊；第三组接触诱导发情的去卵巢山羊。从引入雌性前 8 小时到引入雌性后 8 小时，每 2 小时测定一次公山羊的血浆雄激素浓度。引入发情诱导的山羊显著增加了雄激素浓度，高于隔离的公山羊和接触未处理的山羊（P < 0.05）。在实验 2 中（每组 5 只），一组公山羊从 10 月到 7 月与雌性隔离，而另外两组与去卵巢山羊保持接触，无论是未处理的还是定期诱导发情的。在这三组公山羊中，每月测定一次 10 月、2 月、3 月和 6 月的 LH 血浆浓度，而从 10 月到 7 月每周测定一次雄激素浓度。在正常的季节性无性欲期，三组公山羊的 LH 和雄激素血浆浓度均较低，且组间无差异（P > 0.05）。我们的结论是，与发情诱导的山羊的完全接触和性互动未能阻止公山羊 LH 和雄激素血浆浓度的季节性变化，尽管公山羊可以通过急性增加血浆 LH 和雄激素对雌性的引入做出反应。
