Ndibualonji B B, Dehareng D, Godeau J M
Laboratoire de biochimie, faculté de médecine vétérinaire, université de Liège, Liège-Sart Tilman, Belgique.
Reprod Nutr Dev. 1995;35(2):137-54.
In order to study the effects of a nitrogenous and/or energetic underfeeding on some metabolites and hormones, 4 dry cows were fed in 2 equal daily meals with hay-based rations. Four rations were distributed. They supplied too much (HN) or too little (LN) digestible protein in the small intestine and too much (HE) or too little (LE) net energy, ie the diets were HN-HE, HN-LE, LN-HE, and LN-LE. Continuous collection of rumen liquor samples (volatile fatty acids or VFA determination), venous blood samples (amino acids (alanine Ala, glutamine Gln, glycine Gly and serine Ser), urea, glucose, insulin and growth hormone (GH) measurements) and urine samples (determination of the amount of 3-methylhistidine 3-MeHi excreted) was carried out for 24 consecutive hours. By comparison with the reference diet (HN-HE), underfeeding was accompanied by a reduction in ruminal VFA concentrations, an increase in those of plasma Gly and GH, and a maintenance of glycemia levels. Furthermore, nitrogenous and energetic underfeeding (LN-LE) was accompanied by a decrease in plasma Ala, Gln and insulin concentrations. Nitrogenous underfeeding (LN-HE) caused a decrease in uremia levels, an increment in those of serinemia and no variation in circulating insulin concentrations. The energetic underfeeding (HN-LE) was accompanied by a reduction in insulinemia levels and an increase in those of alaninemia and serinemia. Such changes suggest that dry cattle adapt to underfeeding by mobilizing endogenous proteins. However, only the 2 diets with reduced energetic supplies were accompanied by an increase (P < 0.05) in the amount of the urinary 3-MeHi excreted per 24 h, suggesting that the level of energy in the diet is the main trigger for protein mobilization. Finally, the study of the 24-h evolution of the parameters revealed the influence of the feeding time (morning or evening) and the level of the dietary nitrogen and energy supplied on the variation in their concentration.
为了研究含氮和/或能量摄入不足对某些代谢物和激素的影响，4头干奶牛每天分两顿等量投喂以干草为基础的日粮。共分配了四种日粮。它们在小肠中提供了过多（HN）或过少（LN）的可消化蛋白质以及过多（HE）或过少（LE）的净能量，即日粮分别为HN-HE、HN-LE、LN-HE和LN-LE。连续24小时采集瘤胃液样本（测定挥发性脂肪酸或VFA）、静脉血样本（测定氨基酸（丙氨酸Ala、谷氨酰胺Gln、甘氨酸Gly和丝氨酸Ser）、尿素、葡萄糖、胰岛素和生长激素（GH））以及尿液样本（测定排泄的3-甲基组氨酸3-MeHi的量）。与对照日粮（HN-HE）相比，摄入不足伴随着瘤胃VFA浓度降低、血浆Gly和GH浓度升高以及血糖水平维持稳定。此外，含氮和能量摄入不足（LN-LE）伴随着血浆Ala、Gln和胰岛素浓度降低。含氮摄入不足（LN-HE）导致尿素水平降低、血清丝氨酸水平升高且循环胰岛素浓度无变化。能量摄入不足（HN-LE）伴随着胰岛素血症水平降低以及丙氨酸血症和血清丝氨酸血症水平升高。这些变化表明干奶牛通过动员内源性蛋白质来适应摄入不足。然而，只有能量供应减少的两种日粮伴随着每24小时排泄的尿3-MeHi量增加（P<0.05），这表明日粮中的能量水平是蛋白质动员的主要触发因素。最后，对这些参数24小时变化的研究揭示了投喂时间（早上或晚上）以及日粮中氮和能量供应水平对其浓度变化的影响。
