中文摘要：

本研究先后通过2个梯度试验来研究低蛋白质饲粮条件下生长猪对色氨酸的需要量。试验分别选取360头平均初始体重为（24.16±2.35）kg和（23.60±2.17）kg的＂杜×长×大＂三元杂交健康生长猪,随机分为6个处理,每个处理6个重复,每个重复10头猪。对照组饲粮参照NRC（1998）猪营养需要量推荐标准设计,蛋白质含量为正常水平;试验组饲粮的蛋白质水平较对照组饲粮降低4个百分点,各试验组的真可消化赖氨酸、真可消化蛋氨酸、真可消化苏氨酸的含量和净能水平保持一致;试验1中真可消化色氨酸设0.131%、0.146%、0.161%、0.176%和0.191%5个水平,试验2中真可消化色氨酸设0.141%、0.150%、0.159%、0.170%和0.181%5个水平;对照组饲粮真可消化赖氨酸、含硫氨基酸、真可消化苏氨酸含量和净能水平与试验组接近。结果表明,在氨基酸平衡时,饲粮蛋白质水平较NRC（1998）猪营养需要量推荐标准降低4个百分点并不影响试猪的生长性能;折线模型和二次回归分析结果显示,低蛋白质饲粮中真可消化色氨酸水平为0.146%时,试猪可获得最佳生长性能,超过0.152%时,试猪的生长性能有降低趋势,饲粮中真可消化赖氨酸与色氨酸的适宜比例为100∶（17.6～18.3）。结果提示,饲粮蛋白质水平较NRC（1998）猪营养需要量推荐标准降低4个百分点,回肠真可消化赖氨酸为0.83%时,真可消化色氨酸水平为0.146%可以较好满足生长猪（20～50 kg）的生长需要。

英文摘要：

Two experiments were conducted to determine requirements of tryptophan（Trp） for growing pigs fed low protein diets supplemented with crystalline amino acids（CAA）.A total of 360 cross-bred（Duroc×Landrace×Large white） growing pigs [（24.16±2.35） kg,experiment 1] or 360 cross-bred（Duroc×Landrace×Large white） growing pigs [（23.60±2.17） kg,experiment 2] were allotted to 6 treatments with 6 replicates in each treatment and 10 growing pigs in each replicate.In experiment 1,the treatments consisted of a corn and soybean meal control diet meeting the nutrient requirements of swine（NRC,1998） and five test diets with the same low protein content（4% reduction） and five different Trp levels（0.131%,0.146%,0.161%,0.176% and 0.191%,respectively） supplemented with CAA.In experiment 2,a control diet was the same as that in the experiment 1,and five test diets had the same low protein content（4% reduction） and five different Trp levels（0.141%,0.150%,0.159%,0.170%,and 0.181%,respectively）.The results showed that no adverse effects on growth performance were found in growing pigs fed the low protein（4% reduction） diets with CAA supplementation.The results of broken line model and quadratic regression analysis indicated that to achieve maximum growth performance in growing pigs,0.146% Trp in the low protein（4% reduction） diet with CAA supplementation was necessary,but not greater than 0.152%,and TDLys：TDTrp = 100：（17.6 to 18.3） was a suitable scope.The results indicate that feeding a low protein（4% reduction） diet,optimum growth performance of growing pigs（20 to 50 kg） will be obtained if the diet provides 0.146% Trp,as well as 0.83% ileum true digestible lysine.