摘要The hypothesis that capping dietary starch:protein ratios would enhance the performance of broiler chickens offered reduced-crude protein(CP)diets was tested in this experiment.A total of 432 off-sex,male Ross 308 chicks were allocated to 7 dietary treatments from 7 to 35 d post-hatch.The experimental design consisted of a 3 × 2 factorial array of treatments with the seventh treatment serving as a positive control.Three levels of dietary CP(197.5,180.0 and 162.5 g/kg)with either uncapped or capped dietary starch:protein ratios constituted the factorial array of treatments,whilst the positive control diet con-tained 215.0 g/kg CP.The positive control diet had an analysed dietary starch:protein ratio of 1.50 as opposed to a ratio of 1.68 in the uncapped 197.5 g/kg CP diet and 1.41 in the corresponding capped diet and the capped 197.5 g/kg CP diet displayed promise.The growth performance this diet matched the positive control but outperformed the uncapped 197.5 g/kg CP diet by 10.4％(2,161 vs.1,958 g/bird;P = 0.009)in weight gain,by 3.10％(3,492 vs.3,387 g/bird;P = 0.019)in feed intake on the basis of pair-wise comparisons and numerically improved FCR by 4.04％(1.616 vs.1.684).However,the growth per-formance of birds offered the 180.0 and 162.5 g/kg CP dietary treatments was remarkably inferior,irre-spective of dietary starch:protein ratios.This inferior growth performance was associated with poor feathering and even feather-pecking and significant linear relationships between feather scores and pa-rameters of growth performance were observed.The amino acid profile of feathers was determined where cysteine,glutamic acid,glycine,proline and serine were dominant in a crude protein content of 931 g/kg.Presumably,the feathering issues observed were manifestations of amino acid inadequacies or imbalances in the more reduced-CP diets and consideration is given to the implications of these outcomes.