本试验旨在研究不同粗蛋白质(CP)水平饲粮添加外源蛋白酶对肉鸡生产性能、血清生化指标和抗氧化功能的影响。采用3×3双因素试验设计,即3种CP水平,分别为正对照(PC,CP水平1~21 d为21%,22~42 d为19%)、负对照1(NC1,CP水平在PC基础上降1%)和负对照2(NC2,CP水平在PC基础上降2%);3种蛋白酶添加水平(0、150和300 mg/kg)。选取1 080只1日龄爱拔益加(AA)肉鸡,随机分为9个处理,每个处理6个重复,每个重复20只鸡,公母各占1/2。试验期42 d。结果表明:1)CP水平对肉鸡平均体重(ABW)、平均日增重(ADG)、平均日采食量(ADFI)和料重比(F/G)有显著影响(P<0.05)。当CP水平从PC降至NC2时,ABW和ADG显著降低(P<0.05),F/G显著增加(P<0.05);蛋白酶水平对F/G有显著影响(P<0.05),300 mg/kg蛋白酶处理显著降低了肉鸡1~21 d的F/G(P<0.05)。2)CP水平对血清白蛋白和球蛋白含量有显著影响(P<0.05),PC处理42 d血清白蛋白含量显著高于NC2处理(P<0.05),血清球蛋白含量显著高于NC1处理(P<0.05);蛋白酶水平对血清肌酐含量有显著影响(P<0.05),300 mg/kg蛋白酶处理21 d血清肌酐含量显著降低(P<0.05);蛋白酶水平和CP水平的互作对21 d血清总蛋白和球蛋白含量有显著影响(P<0.05)。3)CP水平对血清中谷胱甘肽过氧化物酶(GSH-Px)活性有显著影响(P<0.05),PC处理42 d血清GSH-Px活性显著高于NC2处理(P<0.05);蛋白酶水平对血清GSH-Px活性和丙二醛(MDA)含量有显著影响(P<0.05),与不加酶处理相比,300 mg/kg蛋白酶处理21 d血清GSH-Px活性显著升高(P<0.05),血清MDA含量显著降低(P<0.05)。由此可见,饲粮CP水平降低1%后添加300 mg/kg蛋白酶对肉鸡生产性能、血清生化指标和抗氧化功能无影响,在基础饲粮中直接添加300 mg/kg蛋白酶效果更佳。

The experiment was conducted to investigate the effects of different crude protein (CP) levels diet supplemented with exogenous protease on performance, serum biochemical indices and antioxidant function of broilers. A 3×3 factorial design with 3 CP levels (21%, 20% and 19% at 1 to 21 days, 19%, 18% and 17% at 22 to 42 days) and 3 protease levels (0, 150 and 300 mg/kg). High CP diet without protease was a positive control (PC) treatment, low CP diets were two negative control (NC1 and NC2) treatments. A total of 1 080 one-day-old Arbor Acres (AA) broilers were randomly assigned to 9 treatments with 6 replicates per treatment and 20 broilers per replicate (half male and half female). The experiment lasted for 42 days. The results showed as follows: 1) CP levels had significant effects on feed-to-gain ratio (F/G), average body weight (ABW), average daily gain (ADG) and average daily feed intake (ADFI) of broilers (P<0.05), when the dietary CP levels was reduced from PC to NC2, ABW and ADG were significantly reduced (P<0.05), F/G was significantly increased (P<0.05). Protease level had significant effects on F/G (P<0.05), 300 mg/kg protease supplementation significantly reduced F/G of broilers at 1 to 21 days. 2) CP levels had significantly effects on the content of albumin and globulin in serum (P<0.05). The serum albumin content of broilers at 42 days in PC treatment was significantly higher than that in NC2 treatment (P<0.05), and the serum globulin content was significantly higher than that of NC1 treatment (P<0.05). Protease level had significant effects on serum creatinine content (P<0.05), 300 mg/kg protease supplementation significantly reduced serum creatinine content of broilers at 21 days (P<0.05). The interaction between protease level and CP level had significantly effects on the content of total protein and globulin in serum of broilers at 21 days (P<0.05). 3) CP levels had significantly effect on serum glutathione peroxidase (GSH-Px) activity (P<0.05), the serum GSH-Px activity of broilers at 42 days in PC treatment was significantly higher than that in NC2 treatment (P<0.05), protease level had significantly effect on serum GSH-Px activity and malondialdehyde (MDA) content; compared with the group without enzymes, serum GSH-Px activity was increased significantly and serum MDA content was decreased significantly in 300 mg/kg protease supplementation treatment (P<0.05). In conclusion, when dietary CP levels is reduced 1%, 300 mg/kg protease supplementation has no effects on performance, serum biochemical indices and antioxidant function of broilers, and 300 mg/kg protease supplementation in basal diets has a better effect.