Short R E, Staigmiller R B, Bellows R A, Ford S P
Fort Keogh Livestock and Range Research Laboratory, ARS, USDA, Miles City, MT 59301.
J Anim Sci. 1995 Jan;73(1):198-205. doi: 10.2527/1995.731198x.
Pregnant cows were fed pine needles (PN, 2 kg.cow-1.d-1) mixed with the diet to determine factors that affect abortion response. In Exp. 1, treatments were used to determine the effects of experimental stress and pelleting of pine needles. Pelleting needles and experimental stress delayed abortion response (P < .01). Stress-induced delay was associated with abnormal patterns of progesterone and cortisol (P < .01). In Exp. 2A and 2B, the role of the corpus luteum (CL) in abortion response to PN consumption was investigated by regressing the CL with prostaglandin F2 alpha. Regression of the CL and PN feeding reduced interval to parturition, but the effect of PN feeding was less when the CL was regressed (PN x CL, P < .01). The progesterone increase in response to experimental stress was decreased by CL regression (P < .01). In Exp. 3, melengestrol acetate (MGA) was fed (0, 2, or 4 mg.cow-1.d-1) in addition to PN. Parturition was blocked more effectively as dose of MGA increased (P = .075), but only parturition was blocked rather than the effects of PN. In Exp. 4, CL regression was blocked by feeding ketoprofen. Ketoprofen delayed response to PN, but the effect was only temporary (P < .01). Our conclusions are that 1) experimental stress delays abortion response to PN by increased concentrations of progesterone, 2) pelleting PN decreases their abortifacient activity, and 3) abortions caused by PN can be blocked by feeding a progestin or a prostaglandin inhibitor, but these compounds do not block the primary abortifacient effects of PN.
给怀孕母牛喂食与日粮混合的松针（PN，2千克/头/天），以确定影响流产反应的因素。在实验1中，采用不同处理来确定实验应激和松针制粒的影响。松针制粒和实验应激会延迟流产反应（P < 0.01）。应激诱导的延迟与孕酮和皮质醇的异常模式有关（P < 0.01）。在实验2A和2B中，通过用前列腺素F2α使黄体退化，研究了黄体（CL）在对食用PN的流产反应中的作用。黄体退化和PN喂养缩短了分娩间隔，但当黄体退化时，PN喂养的效果较小（PN×CL，P < 0.01）。黄体退化降低了实验应激引起的孕酮升高（P < 0.01）。在实验3中，除了PN外，还喂食醋酸甲孕酮（MGA，0、2或4毫克/头/天）。随着MGA剂量增加，分娩阻断更有效（P = 0.075），但仅阻断了分娩，而非PN的作用。在实验4中，通过喂食酮洛芬来阻断黄体退化。酮洛芬延迟了对PN的反应，但效果只是暂时的（P < 0.01）。我们的结论是：1）实验应激通过增加孕酮浓度延迟对PN的流产反应；2）松针制粒会降低其堕胎活性；3）PN引起的流产可通过喂食孕激素或前列腺素抑制剂来阻断，但这些化合物不会阻断PN的主要堕胎作用。
