Short R E, Bellows R A, Staigmiller R B, Berardinelli J G, Custer E E
U. S. Department of Agriculture, Miles City, MT 59301.
J Anim Sci. 1990 Mar;68(3):799-816. doi: 10.2527/1990.683799x.
Postpartum infertility is caused by four factors: general infertility, lack of uterine involution, short estrous cycles and anestrus. The general infertility component is common to any estrous cycle and reduces potential fertility by 20 to 30%. Incomplete uterine involution prevents fertilization during the first 20 d after calving but is not related to anestrus. Short estrous cycles prevent fertility during the first 40 d after calving by causing the cow to return to estrus before pregnancy recognition occurs. Anestrus is the major component of postpartum infertility and is affected by several minor factors: season, breed, parity, dystocia, presence of a bull, uterine palpation and carryover effects from the previous pregnancy as well as two major factors: suckling and nutrition. These major factors have direct effects on anestrus but also interact with one or more other factors to control postpartum anestrus. Physiological mechanisms associated with anestrus involve blockage of the GnRH "pulse generator" in the hypothalamus, but other pathways also must be involved because bypassing the pulse generator is not an effective treatment for all cows. The primary cause of anestrus probably is different for different stages of anestrus. The mediating mechanisms for anestrus are not involved with prolactin, oxytocin, the adrenal or direct neural input from the mammary gland but are at least partially involved with blood glucose and the endogenous opioid peptide system. Management options to decrease the impact of anestrus and infertility include: 1) restrict breeding season to less than or equal to 45 d; 2) manage nutrition so body condition score is 5 to 7 before calving; 3) minimize effects of dystocia and stimulate estrous activity with a sterile bull and estrous synchronization; and 4) judicious use of complete, partial or short-term weaning.
一般性不孕、子宫复旧不全、发情周期短和乏情。一般性不孕因素在任何发情周期中都常见，会使潜在繁殖力降低20%至30%。子宫复旧不全在产犊后的前20天内会妨碍受精，但与乏情无关。发情周期短会使母牛在产犊后的前40天内因在妊娠识别发生前就再次发情而无法受孕。乏情是产后不孕的主要因素，受几个次要因素影响：季节、品种、胎次、难产、公牛的存在、子宫触诊以及前次妊娠的遗留影响，还有两个主要因素：哺乳和营养。这些主要因素对乏情有直接影响，还会与一个或多个其他因素相互作用以控制产后乏情。与乏情相关的生理机制涉及下丘脑促性腺激素释放激素（GnRH）“脉冲发生器”的阻断，但其他途径也必定参与其中，因为绕过脉冲发生器并非对所有母牛都是有效的治疗方法。不同阶段乏情的主要原因可能不同。乏情的介导机制与催乳素、催产素、肾上腺或来自乳腺的直接神经输入无关，但至少部分与血糖和内源性阿片肽系统有关。减少乏情和不孕影响的管理措施包括：1）将配种季节限制在小于或等于45天；2）管理营养，使产犊前体况评分为5至7；3）尽量减少难产的影响，用无菌公牛和同期发情刺激发情活动；4）明智地使用完全、部分或短期断奶。
