Schroeder G F, Titgemeyer E C, Awawdeh M S, Smith J S, Gnad D P
Department of Animal Sciences and Industry, Kansas State University, Manhattan, 66506-1600, USA.
J Anim Sci. 2006 Jun;84(6):1497-504. doi: 10.2527/2006.8461497x.
We evaluated the effect of energy supplementation on Met use in growing steers. Six ruminally cannulated Holstein steers (228 +/- 8 kg of BW) were used in a 6 x 6 Latin square and fed 2.8 kg of DM/d of a diet based on soybean hulls. Treatments were abomasal infusion of 2 amounts of Met (0 or 3 g/d) and supplementation with 3 amounts of energy (0, 1.3, or 2.6 Mcal of GE/d) in a 2 x 3 factorial arrangement. The 1.3 Mcal/d treatment was supplied through ruminal infusion of 90 g/d of acetate, 90 g/d of propionate, and 30 g/d of butyrate, and abomasal infusion of 30 g/d of glucose and 30 g/d of fat. The 2.6 Mcal/d treatment supplied twice these amounts. All steers received basal infusions of 400 g/d of acetate into the rumen and a mixture (125 g/d) containing all essential AA except Met into the abomasum. No interactions between Met and energy levels were observed. Nitrogen balance was increased (P < 0.05) by Met supplementation from 23.6 to 27.8 g/d, indicating that protein deposition was limited by Met. Nitrogen retention increased linearly (P < 0.05) from 23.6 to 27.7 g/d with increased energy supply. Increased energy supply also linearly reduced (P < 0.05) urinary N excretion from 44.6 to 39.7 g/d and reduced plasma urea concentrations from 2.8 to 2.1 mM. Total tract apparent OM and NDF digestibilities were reduced linearly (P < 0.05) by energy supplementation, from 78.2 and 78.7% to 74.3 and 74.5%, respectively. Whole-body protein synthesis and degradation were not affected significantly by energy supplementation. Energy supplementation linearly increased (P < 0.05) serum IGF-I from 694 to 818 ng/mL and quadratically increased (P < 0.05) serum insulin (0.38, 0.47, and 0.42 ng/mL for 0, 1.3, and 2.6 Mcal/d, respectively). In growing steers, N retention was improved by energy supplementation, even when Met limited protein deposition, suggesting that energy supplementation affects the efficiency of AA use.
我们评估了能量补充对生长育肥牛蛋氨酸（Met）利用的影响。选用6头安装了瘤胃瘘管的荷斯坦育肥牛（体重228±8千克），采用6×6拉丁方设计，给它们饲喂以大豆皮为基础的日粮，每天每头2.8千克干物质（DM）。处理方式为真胃灌注2种剂量的蛋氨酸（0或3克/天），并以2×3析因设计补充3种剂量的能量（0、1.3或2.6兆卡消化能/天）。1.3兆卡/天的处理组通过瘤胃灌注每天90克乙酸盐、90克丙酸盐和30克丁酸盐，以及真胃灌注每天30克葡萄糖和30克脂肪来提供能量。2.6兆卡/天的处理组提供的量是前者的两倍。所有育肥牛瘤胃每天基础灌注400克乙酸盐，真胃灌注一种混合物（每天125克），该混合物包含除蛋氨酸外的所有必需氨基酸。未观察到蛋氨酸和能量水平之间的交互作用。补充蛋氨酸使氮平衡从23.6克/天增加到27.8克/天（P<0.05），这表明蛋白质沉积受蛋氨酸限制。随着能量供应增加，氮保留量从23.6克/天线性增加到27.7克/天（P<0.05）。能量供应增加还使尿氮排泄量从44.6克/天线性减少到39.7克/天（P<0.05），血浆尿素浓度从2.8毫摩尔/升降低到2.1毫摩尔/升。能量补充使全消化道表观有机物和中性洗涤纤维消化率分别从78.2%和78.7%线性降低到74.3%和74.5%（P<0.05）。能量补充对全身蛋白质合成和降解没有显著影响。能量补充使血清胰岛素样生长因子-I（IGF-I）从694纳克/毫升线性增加到818纳克/毫升（P<0.05），使血清胰岛素呈二次曲线增加（P<0.05）（0、1.3和2.6兆卡/天的处理组血清胰岛素分别为0.38、0.47和0.42纳克/毫升）。在生长育肥牛中，即使蛋氨酸限制蛋白质沉积，能量补充仍能改善氮保留，这表明能量补充会影响氨基酸的利用效率。
