Huntington G B, Reynolds P J, Tyrrell H F
J Dairy Sci. 1983 Sep;66(9):1901-8. doi: 10.3168/jds.S0022-0302(83)82028-1.
Objectives were to define daily patterns of net absorption of various nutrients and to assess effects of intraruminal infusion of acetic acid on concentrations of ruminal fluid and net absorption of various metabolites. These characteristics were measured in three nonpregnant, dry Holstein cows (491 kg) at hourly intervals for 24 h before and after 5 days of intraruminal infusion of acetic acid to provide energy equal to 10% of daily intake of metabolizable energy. Cows were fed a completely mixed, 60% corn silage, 40% grain supplement diet at maintenance intake; daily rations were split into two feedings. Net rates of absorption were greatest after feeding and least during early morning. Net absorption of all metabolites measured was similar for the two daily feeding intervals, indicating daily net absorption could be calculated from either feeding interval. Intraruminal infusion of acetic acid caused increased ruminal and plasma concentrations of acetate, increased net absorption of acetate, and almost a twofold increased loss of urea-nitrogen from plasma to the gut. Sixty-nine percent of acetic acid infused was accounted for by increased net absorption of acetate. Ruminal fluid concentrations and net absorption of other volatile fatty acids were not affected by infusion of acetic acid. Net absorptions of ammonia-nitrogen, L-lactate, and glucose likewise were not affected. Net absorption of volatile fatty acid and L-lactate was 43% of daily intake of metabolizable energy.
目的是确定各种养分的净吸收每日模式，并评估瘤胃内注入乙酸对瘤胃液浓度和各种代谢物净吸收的影响。在3头未怀孕的干奶期荷斯坦奶牛（体重491千克）中进行这些特性的测量，在瘤胃内注入乙酸5天以提供相当于每日可代谢能量摄入量10%的能量之前和之后，每隔1小时测量24小时。奶牛按维持摄入量饲喂完全混合的日粮，其中60%为玉米青贮，40%为谷物补充料；每日日粮分为两次投喂。净吸收速率在喂食后最大，在清晨最小。在两个每日投喂间隔期间，所测量的所有代谢物的净吸收相似，这表明可以从任一投喂间隔计算每日净吸收量。瘤胃内注入乙酸导致瘤胃和血浆中乙酸浓度增加，乙酸净吸收增加，并且从血浆到肠道的尿素氮损失几乎增加了两倍。注入的乙酸中有69%可通过乙酸净吸收增加来解释。瘤胃液中其他挥发性脂肪酸的浓度和净吸收不受乙酸注入的影响。氨氮、L-乳酸和葡萄糖的净吸收同样不受影响。挥发性脂肪酸和L-乳酸的净吸收量为每日可代谢能量摄入量的43%。
