Schwab C G, Muise S J, Hylton W E, Moore J J
J Dairy Sci. 1982 Oct;65(10):1950-61. doi: 10.3168/jds.S0022-0302(82)82444-2.
Three abomasal infusion trials were to determine the first-limiting amino acid for nitrogen retention of postweaned Holstein bull calves fed a starter ration based on cereal by-product feeds. Ration ingredients contributed the following percentages of total amino acids: wheat middlings 38, brewer's grains 24, hominy feed 21, oat hulls 10, distiller's grains 6, and molasses 1. Dry matter of the pelleted ration contained 13 to 14% crude protein and .23 to .26% sulfur. Each trial was a replicated 4 x 4 Latin square with 9-day periods. Calves were weaned at 4 wk and infusions initiated at 5 to 6 wk of age. Abomasal infusion of the 10 essential amino acids, an isonitrogenous quantity of an equimolar mixture of alanine, asparagine, glutamate, glycine, and serine, or an isocaloric quantity of glucose indicated that essential amino acid(s) rather than nonspecific nitrogen or energy was limiting protein synthesis. Quadratic responses in urine nitrogen excretion and retained nitrogen occurred when 0, .3, .6, and 1.2 g L-methionine/kg starter ration were infused. Greatest responses occurred with .6 g methionine, which increased retained nitrogen 11 and 19% and decreased urine nitrogen 7 and 10%. The relationship between infused methionine and plasma methionine was linear. Infusions in all trials had no effect on digestibility of energy and nitrogen.
进行了三项皱胃灌注试验，以确定以谷物副产品饲料为基础的开食料喂养的断奶后荷斯坦公牛犊牛氮保留的第一限制性氨基酸。日粮成分在总氨基酸中所占百分比为：小麦麸38%、啤酒糟24%、玉米糁21%、燕麦壳10%、酒糟6%、糖蜜1%。颗粒日粮的干物质含有13%至14%的粗蛋白和0.23%至0.26%的硫。每项试验为重复的4×4拉丁方设计，每期9天。犊牛在4周龄断奶，在5至6周龄开始灌注。皱胃灌注10种必需氨基酸、等氮量的丙氨酸、天冬酰胺、谷氨酸、甘氨酸和丝氨酸的等摩尔混合物或等热量的葡萄糖，结果表明，限制蛋白质合成的是必需氨基酸而非非特异性氮或能量。当向每千克开食料中灌注0、0.3、0.6和1.2克L-蛋氨酸时，尿氮排泄量和氮保留量出现二次反应。最大反应出现在灌注0.6克蛋氨酸时，此时氮保留量增加了11%和19%，尿氮量减少了7%和10%。灌注的蛋氨酸与血浆蛋氨酸之间的关系呈线性。所有试验中的灌注对能量和氮的消化率均无影响。
