Graded quantities of 1.38, 2.76 and 4.14 g/kg L-methionine were included in a control diet formulated to contain 3.07 g/kg digestible methionine. Each of the 4 dietary treatments was offered to 6 replicate cages (initially 8 birds per cage) from 1 to 21 d post–hatch. The parameters assessed included growth performance, nutrient utilisation (apparent metabolisable energy [AME], AME:GE ratios, N retention, N-corrected apparent metabolisable energy [AMEn]), apparent digestibility coefficients and disappearance rates of amino acids in the distal ileum. They also included free amino concentrations in systemic plasma (brachial vein) at 20 d post–hatch and in hepatic tissue at 14 and 21 d post–hatch. Graded L-methionine inclusions quadratically influenced weight gain (r = 0.688; P = 0.001) and FCR (r = 0.780; P < 0.001). It may be deduced from the quadratic regressions that 3.43 g/kg L-methionine supported maximum weight gain of 1,036 g/kg and 3.50 g/kg L-methionine minimum FCR of 1.193, from 1 to 21 d post–hatch. The control diet contained specified levels of 3.07 g/kg digestible methionine and 13.0 g/kg digestible lysine. Thus, an inclusion of 3.465 g/kg L-methionine corresponded to a total of 6.535 g/kg methionine or a methionine-to-lysine ratio of 50.3, which is higher than standard recommendations. The implications of this and other outcomes of the present study are reported and discussed.

将 1.38、2.76 和 4.14 g/kg L-蛋氨酸的分级量包含在配制为含有 3.07 g/kg 可消化蛋氨酸的对照饮食中。从孵化后 1 天到 21 天，将 4 种饮食处理中的每一种提供给 6 个重复的笼子（最初每个笼子 8 只鸟）。评估的参数包括生长性能、养分利用率（表观代谢能 [AME]、AME:GE 比率、N 保留、N 校正表观代谢能 [AMEn]）、表观消化率系数和远端回肠中氨基酸的消失率。它们还包括孵化后 20 天全身血浆（臂静脉）和孵化后 14 天和 21 天肝组织中的游离氨基浓度。分级 L-蛋氨酸夹杂物对体重增加的影响呈二次方关系 ( r  = 0.688; P = 0.001) 和 FCR ( r  = 0.780; P  < 0.001)。可以从二次回归中推断出，3.43 g/kg L-蛋氨酸支持最大体重增加 1,036 g/kg，3.50 g/kg L-蛋氨酸支持 1.193 的最小 FCR，从孵化后 1 天到 21 天。对照饮食含有指定水平的 3.07 g/kg 可消化蛋氨酸和 13.0 g/kg 可消化赖氨酸。因此，包含 3.465 g/kg L-蛋氨酸对应于总共 6.535 g/kg 蛋氨酸或 50.3 的蛋氨酸与赖氨酸比，高于标准建议。报告和讨论了本研究的这一结果和其他结果的影响。