This experiment was conducted to investigate the effects of low-protein amino acid-supplemented diets on growth performance, serum biochemical indices and fecal nitrogen content of Beijing ducks. Four hundred and fifty one-day-old Beijing ducks were randomly allocated to 3 groups with 5 replicates per group and 30 ducks per replicate. Diets were prepared with 2-phase feeding program. Three diets were formulated for each phase. The control group was fed diets with crude protein level of 20% during 1 to 14 days of age and 18% during 15 to 42 days of age. The experimental groups I and II were fed diets with the crude protein levels of 1 and 2 percentages less than the control diet, respectively, but supplemented amino acids. The results showed as follows: 1) there were no significant differences in average daily feed intake, average daily gain and feed/ gain among 3 groups during 1 to 14, 15 to 42 and 1 to 42 days of age (P >0.05). 2) At 14 and 42 days of age, no significant differences in serum total protein, uric acid and urea nitrogen contents, and alanine amin-otransferase and glutamic-oxaloacetic transaminase activities were found among 3 groups (P > 0. 05). 3) Compared with the control group, the fecal nitrogen content in experimental groups I and II was reduced by 4.60% and 15. 71% at 1 to 14 days of age and by 10. 77% and 15. 82% at 15 to 42 days of age (P < 0.05) , respectively. It is concluded that reducing dietary crude protein level by 1 to 2 percentages has no significant effects on growth performance and serum biochemical indices, while significantly decreases fecal nitrogen content of Beijing ducks under the premise of meeting the amino acid requirements.%本试验旨在研究低蛋白质补充氨基酸饲粮对北京鸭生长性能、血清生化指标及粪氮含量的影响.选取1日龄北京鸭450只,随机分为3组,每组5个重复,每个重复30只.饲粮分2个阶段配制,每个阶段配制3种饲粮.对照组1～ 14日龄和15～42日龄分别饲喂粗蛋白质水平为20％和18％的饲粮；试验Ⅰ组、试验Ⅱ组饲喂在对照组饲粮基础上分别降低1、2个百分点的低蛋白质补充氨基酸饲粮.试验期42 d.结果表明:1)1～14日龄、15～42日龄及1～42日龄平均日采食量、平均日增重及料重比各组间均无显著差异(P＞0.05).2)14日龄、42日龄血清总蛋白、尿素氮、尿酸含量以及谷丙转氨酶及谷草转氨酶活性各组间均无显著差异(P＞0.05).3)试验Ⅰ组、试验Ⅱ组的1 ～ 14日龄及15～42日龄粪氮含量分别比对照组下降了4.60％、15.71％及10.77％、15.82％,差异均显著(P＜0.05).由此可见,在满足氨基酸需要的前提下,降低饲粮粗蛋白质1～2个百分点对北京鸭生长性能、血清生化指标无显著影响,并可显著降低粪氮含量.
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