本试验旨在研究饲粮中不同(蛋氨酸+半胱氨酸)/赖氨酸 比例对肉仔鸡生长性能和经济效益的影响,探讨肉仔鸡饲粮中适宜的(Met+Cys)/Lys比例。选取1日龄罗斯308商品肉仔鸡3 600只,随机分为4个饲粮处理,(Met+Cys)/Lys比例分别为0.64、0.68、0.72和0.76,每个处理3个重复,每个重复300只鸡,公母各占1/2。试验期35 d,测定不同(Met+Cys)/Lys比例对肉仔鸡生长性能、血浆游离氨基酸浓度和经济效益的影响。结果表明,饲粮中不同(Met+Cys)/Lys比例对各日龄阶段肉仔鸡生长性能无显著影响(P>0.05),但饲粮中(Met+Cys)/Lys比例从0.76降低到0.64时,1~35 d肉仔鸡料重比呈线性升高趋势(P=0.05),经济效益逐渐降低,血浆Met和Cys浓度线性降低(P<0.05)。降低饲粮(Met+Cys)/Lys比例,肉仔鸡血浆尿素氮、尿酸、丝氨酸和异亮氨酸浓度显著增加(P<0.05),甘氨酸浓度呈线性升高(P<0.05),酪氨酸浓度呈二次曲线降低趋势(P=0.05),当比例降低到0.68时血浆谷氨酸和氨浓度显著升高(P<0.05)。降低(Met+Cys)/Lys比例对肉仔鸡血浆其他氨基酸和总氨基酸浓度均无显著影响(P>0.05)。结果显示,饲粮中(Met+Cys)/Lys比例为0.76时,肉仔鸡血浆游离氨基酸平衡较好,可获得较高的生长性能,经济效益最好。

This experiment was conducted to determine the effects of the ratio of methionine plus cystine to lysine in diets on growth performance and economic benefits of broiler chickens, and to study the optimum (Met+Cys)/Lys ratio in the diet. A total of 3 600 one-day-old Ross 308 mix-sexed broilers were obtained from a commercial hatchery and randomly divided to 4 dietary treatments with 3 replicates per treatment and 300 broilers (half male, half female) per replicate. Graded levels of methionine were supplemented to obtain digestible (Met+Cys)/Lys ratios of 0.64, 0.68, 0.72 and 0.76 in the diet, respectively. Growth performance, plasma free amino acid concentrations and economic benefits of broiler chickens were determined in the trial. The trial lasted for 35 days. Results showed that dietary (Met+Cys)/Lys ratio had no significant effects on the growth performance of broilers (P>0.05). The feed/gain of broilers aged from 1 to 35 days was linearly increased (P=0.05), but the concentrations of methionine and cystine in plasma were linearly decreased (P<0.05), and the economic benefits were decreased when the dietary (Met+Cys)/Lys ratio decreased from 0.76 to 0.64. The concentrations of urea nitrogen, uric acid, serine and isoleucine in plasma of broilers were significantly increased (P<0.05), and the glycine concentration was linearly increased (P<0.05), but the tyrosine concentration was decreased in a quadratic curve with the decrease of dietary (Met+Cys)/Lys ratio (P=0.05). The concentrations of glutamic acid and ammonia in plasma of broilers were significantly increased when dietary (Met+Cys)/Lys ratio decreased to 0.68 (P<0.05). There were no significant differences in the concentrations of the other amino acids and total amino acids in plasma among all groups (P>0.05). Results suggest that the optimum dietary(Met+Cys)/Lys ratio is 0.76, in which growth performance of broilers is improved, plasma free amino acids are balanceable and economic benefits are better.