Quigley J D, Steen T M, Boehms S I
Department of Animal Science, University of Tennessee, Knoxville 37901.
J Dairy Sci. 1992 Jan;75(1):228-35. doi: 10.3168/jds.S0022-0302(92)77757-1.
Eight ruminally cannulated Holstein bull calves were used in a switchback design to evaluate effects of hay on postprandial changes in ruminal pH, ammonia and VFA, blood ketones, and plasma glucose, NEFA, VFA, and urea N. Calves were fed 4.5 kd/d of calf starter with or without hay for ad libitum consumption. Blood and ruminal fluid were sampled every 2 h for 12 h on d 21 (periods 1 and 2) or d 13 (period 3). Ruminal pH declined from 6.6 at 0 h to 5.3 by 2 h. Changes in ruminal and plasma VFA were consistent with low pH and rapid fermentation of soluble carbohydrate. Ruminal ammonia, molar percentage butyrate, and blood ketones, plasma urea N, and plasma molar percentage butyrate were lower when hay was fed. Postprandial increases in blood beta-hydroxybutyrate and acetoacetate were reduced when hay was fed, and correlated .65 and .50, respectively, to ruminal butyrate. Concentration of beta-hydroxybutyrate averaged 1.24 and 1.87 mmol/L at 4 h postfeeding. These data suggest that rapid consumption of limited amounts of grain increased in ruminal VFA and blood ketones; increase in ketones was smaller when hay was included in the diet.
选用8头安装有瘤胃瘘管的荷斯坦公犊牛，采用折返设计来评估干草对餐后瘤胃pH值、氨、挥发性脂肪酸（VFA）、血酮以及血浆葡萄糖、非酯化脂肪酸（NEFA）、VFA和尿素氮变化的影响。给犊牛饲喂4.5千克/天的犊牛开食料，可自由采食，其中一组有干草，另一组没有干草。在第21天（第1和第2阶段）或第13天（第3阶段），每隔2小时采集12小时的血液和瘤胃液样本。瘤胃pH值从0小时的6.6下降到2小时的5.3。瘤胃和血浆VFA的变化与低pH值以及可溶性碳水化合物的快速发酵一致。饲喂干草时，瘤胃氨、丁酸摩尔百分比、血酮、血浆尿素氮和血浆丁酸摩尔百分比较低。饲喂干草时，餐后血液中β-羟基丁酸和乙酰乙酸的增加减少，且分别与瘤胃丁酸的相关性为0.65和0.50。饲喂后4小时，β-羟基丁酸浓度平均为1.24和1.87毫摩尔/升。这些数据表明，快速采食有限量的谷物会增加瘤胃VFA和血酮；日粮中添加干草时，酮的增加幅度较小。
