Ehnert K, Moberg G P
Dept. of Anim. Sci., University of California, Davis 95616.
J Anim Sci. 1991 Jul;69(7):2988-94. doi: 10.2527/1991.6972988x.
The effect of dexamethasone administration, isolation stress, or transportation stress on the ability of exogenous estradiol to induce estrus in progesterone-primed, ovariectomized ewes was evaluated in this study. Dexamethasone administered twice daily over a 6-d period, or a single injection at either 2 h before estradiol administration or 8 h after estradiol treatment, delayed or blocked the expression of estrous behavior. In those animals in which dexamethasone did not block the onset of estrus, the average length of estrus was reduced. Isolation stress, which induced significant increases in the plasma concentration of corticosteroids, failed to significantly alter the number of ewes expressing estrous behavior, although the expression of estrus was blocked in three of the nine treated animals. These nine animals all expressed estrus during the nonstress phase. In contrast to isolation stress, 8 h of transportation not only increased the average plasma concentration of corticosteroids, but also significantly (P less than .05) blocked the expression of estrus in five of eight ewes and delayed the expression of estrus in one other. During the nonstressed control phase, all eight expressed estrus. These findings indicate that management-related stress can block estrogen from inducing estrous behavior, however, the role of the adrenal axis response to stress in blocking estrus remains to be clarified.
本研究评估了地塞米松给药、隔离应激或运输应激对经孕酮预处理的去卵巢母羊中外源性雌二醇诱导发情能力的影响。在6天的时间内每天两次给予地塞米松，或在给予雌二醇前2小时或雌二醇处理后8小时单次注射地塞米松，会延迟或阻止发情行为的表现。在那些地塞米松未阻止发情开始的动物中，发情的平均持续时间缩短。隔离应激导致皮质类固醇血浆浓度显著升高，尽管在9只接受处理的动物中有3只的发情表现被阻断，但未能显著改变表现出发情行为的母羊数量。这9只动物均在非应激阶段表现出发情。与隔离应激相反，8小时的运输不仅增加了皮质类固醇的平均血浆浓度，而且显著（P<0.05）阻断了8只母羊中5只的发情表现，并使另一只母羊的发情表现延迟。在非应激对照阶段，所有8只母羊均表现出发情。这些发现表明，与管理相关的应激可阻止雌激素诱导发情行为，然而，肾上腺轴对应激的反应在阻断发情中的作用仍有待阐明。
