DiCostanzo A, Williams J E, Keisler D H
Department of Animal Science, University of Minnesota, St. Paul 55108, USA.
J Anim Sci. 1999 Nov;77(11):3050-6. doi: 10.2527/1999.77113050x.
Two trials were conducted to evaluate the effects of short- (Trial 1) or long-term (Trial 2) intraruminal isocaloric infusions of acetate or propionate on secretion of LH, insulin, and selected metabolites in short- or long-term energy-restricted beef heifers. In Trial 1, 16 Angus heifers were assigned on d 6 to 12 of a synchronized estrous cycle (estrus = d 0) to a body weight-maintenance (BWM; n = 4) or an energy-restricted, body weight-loss (BWL; n = 12) treatment. On d 12 of a synchronized estrous cycle, heifers received PGF2alpha to synchronize estrus, and 12 h later BWL heifers received intraruminal, isocaloric infusions of acetate, propionate, or vehicle for 6 h and BWM heifers received vehicle concurrently. Mean plasma LH and LH pulse frequencies and amplitudes were not affected by treatment (P > .05). In contrast, infusion of propionate increased plasma insulin (P < .05) and reduced plasma concentration of NEFA (P < .05). In Trial 2, six ovariectomized Angus heifers were energy-restricted for 30 d. On d 14 and 26 of restriction, heifers began receiving intraruminal isocaloric infusions of acetate or propionate for 96 h in a switchback approach. Intraruminal infusions of vehicle for 6 h preceded infusions of acetate or propionate. Jugular blood was collected at 12-min intervals during infusions of vehicle and during the last 6 h of infusion of acetate or propionate. Mean concentration of LH and amplitude of pulses of LH were lower during acetate vs propionate or vehicle infusion (P < .05). Infusion of propionate increased insulin relative to acetate or vehicle infusion (P < .05). Plasma NEFA were reduced by infusion of propionate (P < .05) and increased by infusion of acetate (P < .05).
进行了两项试验，以评估短期（试验1）或长期（试验2）瘤胃内等热量输注乙酸盐或丙酸盐对短期或长期能量受限的育肥牛小母牛促黄体生成素（LH）、胰岛素及选定代谢物分泌的影响。在试验1中，16头安格斯小母牛在同步发情周期的第6至12天（发情期=d0）被分配到体重维持（BWM；n=4）或能量受限、体重减轻（BWL；n=12）处理组。在同步发情周期的第12天，给小母牛注射氯前列醇（PGF2α）以同步发情，12小时后，BWL小母牛接受瘤胃内等热量输注乙酸盐、丙酸盐或载体，持续6小时，BWM小母牛同时接受载体输注。处理对平均血浆LH、LH脉冲频率和幅度没有影响（P>.05）。相反，输注丙酸盐会增加血浆胰岛素（P<.05）并降低血浆非酯化脂肪酸（NEFA）浓度（P<.05）。在试验2中，6头去卵巢的安格斯小母牛能量受限30天。在限制的第14天和第26天，小母牛开始以折返方式接受瘤胃内等热量输注乙酸盐或丙酸盐，持续96小时。在输注乙酸盐或丙酸盐之前，先给小母牛瘤胃内输注载体6小时。在输注载体期间以及输注乙酸盐或丙酸盐的最后6小时内，每隔12分钟采集一次颈静脉血。与输注丙酸盐或载体相比，输注乙酸盐期间LH的平均浓度和脉冲幅度较低（P<.05）。与输注乙酸盐或载体相比，输注丙酸盐会增加胰岛素（P<.05）。输注丙酸盐可降低血浆NEFA（P<.05），输注乙酸盐则会增加血浆NEFA（P<.05）。
