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):1505-11. doi: 10.2527/2006.8461505x.
We evaluated the effects of different supplemental energy sources on Met use in growing steers. Ruminally cannulated Holstein steers were used in two 6 x 6 Latin squares, and data were pooled for analyses. In Exp. 1, steers (148 kg) were fed 2.3 kg of DM/d of a diet based on soybean hulls. Treatments (2 x 3 factorial) were abomasal infusion of 0 or 3 g of l-Met/d, and supplementation with no energy or with glucose (360 g/d) or fat (150 g/d) continuously infused into the abomasum. In Exp. 2, steers (190 kg) received 2.6 kg of dietary DM/d and were provided (2 x 3 factorial) with 0 or 3 g of l-Met/d, and with no supplemental energy or with acetate (385 g/d) or propionate (270 g/ d) continuously infused into the rumen. In both experiments, the energy sources supplied 1.3 Mcal of GE/d, and all steers received basal infusions of 400 g of acetate/d into the rumen and a mixture (125 g/d) of all essential AA except Met into the abomasum. Nitrogen balance (18.8 vs. 23.5 g/d; P < 0.01) and whole-body protein synthesis (2.1 vs. 2.3 kg/d; P < 0.07) were increased by Met supplementation, indicating that protein deposition was limited by Met. Supplemental energy reduced (P < 0.01) urinary N excretion and increased (P < 0.01) N retention without differences among energy sources. Increases in N retention in response to Met were numerically greater when energy was supplemented. Efficiency of supplemental Met use was 11% when no energy was supplemented but averaged 21% when 1.3 Mcal of GE/d was provided. Whole-body protein synthesis and degradation were not affected by energy supplementation. Serum insulin concentrations were increased by glucose and propionate supplementation. Serum IGF-I concentrations were increased by supplementation with Met or glucogenic sources of energy. In growing steers, N retention was increased by energy supplementation even though protein deposition was limited by Met, suggesting that energy supplementation improves the efficiency of AA use. These responses were independent of the source of energy.
我们评估了不同补充能量来源对生长公牛蛋氨酸（Met）利用的影响。在两个6×6拉丁方试验中使用瘤胃插管的荷斯坦公牛，并将数据合并进行分析。在试验1中，给体重148千克的公牛饲喂以大豆皮为基础的日粮，日粮干物质摄入量为2.3千克/天。处理方式（2×3析因设计）包括真胃灌注0或3克/天的L-蛋氨酸，以及真胃持续灌注不补充能量、葡萄糖（360克/天）或脂肪（150克/天）。在试验2中，给体重190千克的公牛饲喂日粮干物质摄入量为2.6千克/天的日粮，并提供（2×3析因设计）0或3克/天的L-蛋氨酸，以及瘤胃持续灌注不补充能量、乙酸盐（385克/天）或丙酸盐（270克/天）。在两个试验中，能量来源提供的消化能均为1.3兆卡/天，所有公牛瘤胃均基础灌注400克/天的乙酸盐，真胃均灌注除蛋氨酸外所有必需氨基酸的混合物（125克/天）。补充蛋氨酸使氮平衡增加（18.8对23.5克/天；P<0.01），全身蛋白质合成增加（2.1对2.3千克/天；P<0.07），表明蛋白质沉积受蛋氨酸限制。补充能量降低了（P<0.01）尿氮排泄，增加了（P<0.01）氮保留，且不同能量来源之间无差异。补充能量时，蛋氨酸增加氮保留的数值更大。不补充能量时，补充蛋氨酸的利用效率为11%，但提供1.3兆卡/天的消化能时，平均利用效率为21%。全身蛋白质合成和降解不受能量补充的影响。补充葡萄糖和丙酸盐使血清胰岛素浓度增加。补充蛋氨酸或生糖能量来源使血清胰岛素样生长因子-I（IGF-I）浓度增加。在生长公牛中，尽管蛋白质沉积受蛋氨酸限制，但补充能量增加了氮保留，这表明补充能量提高了氨基酸利用效率。这些反应与能量来源无关。
