Williams G L
Texas Agricultural Experiment Station, Beeville 78102.
J Anim Sci. 1990 Mar;68(3):831-52. doi: 10.2527/1990.683831x.
An extended and variable period of anovulation and anestrus occurs in suckled beef cows following parturition. This imposes both biological and economic constraints on the efficiency of beef production. A large body of knowledge has linked these phenomena to an attenuation of neuroendocrine signals that subserve gonadal function. During late gestation, high concentrations of placental estrogen inhibit the synthesis of LH, and pituitary stores of LH are depleted at parturition. Maximum pituitary stores of LH, releasable pools of LH and the ability of hypothalamic centers to respond to positive feedback effects of estradiol occur within 3 to 4 wk after calving in suckled cows. However, the requisite pattern of pulsatile LH secretion, which accompanies similar changes in nonsuckled cows within 2 to 3 wk after calving, occurs in only 30 to 50% of suckled animals. The period of acyclicity that continues in the remainder is exacerbated by poor body condition and may persist in some females for periods exceeding 100 d. Utilizing data from the cow, as well as other species, a model for suckling-induced inhibition of pulsatile LH release is proposed. The biological and economic impact of current and future techniques for controlling suckling-induced anestrus also is considered, including a conceptual analysis of nonbiological limitations.
哺乳期肉用母牛产后会出现一段延长且多变的无排卵和乏情期。这对牛肉生产效率造成了生物学和经济方面的限制。大量知识已将这些现象与维持性腺功能的神经内分泌信号减弱联系起来。在妊娠后期，高浓度的胎盘雌激素会抑制促黄体生成素（LH）的合成，且垂体中LH的储备在分娩时会耗尽。哺乳期母牛在产犊后3至4周内，垂体中LH的最大储备量、LH的可释放池以及下丘脑中心对雌二醇正反馈作用的反应能力会出现。然而，产犊后2至3周内非哺乳期母牛出现的类似变化所伴随的必要LH脉冲分泌模式，仅在30%至50%的哺乳期动物中出现。其余母牛的无发情周期因身体状况不佳而加剧，并且在一些母牛中可能会持续超过100天。利用母牛以及其他物种的数据，提出了一种哺乳诱导的LH脉冲释放抑制模型。还考虑了当前和未来控制哺乳诱导乏情技术的生物学和经济影响，包括对非生物学限制的概念分析。
