| This study was performed to evaluate the effects of different doses of Artemisia annua L.aqueous extract(AAE)on growth performance,immune and antioxidative function of broilers.And the molecular mechanism of AAE action was preliminarily explored from the related gene expression of immune and antioxidative indexes,in order to provide a basis for the application of AAE in broiler production.A total of 240 one-day-old Arbor Acres(AA)broilers were randomly divided into 6 treatments with 5 replicates and 8 birds per replicates(half male and female).Broilers in the six groups were offered basal diet supplemented with 0,500,1000,1500,2000 mg/kg AAE and 50 mg/kg chlortetracycline(CTC),respectively.The 42-d experiment included grower period(d 1-21)and finisher period(d 22-42).The study consisted of 3 parts:Part 1:The final body weight(FBW),feed intake(FI)and surplus feed were measured,to calculate the FI and feed conversion efficiency(FE)of each replicate on d 21 and 42.The results showed that the FBW of 1500 mg/kg AAE group was higher than that of the control group on d 21(P<0.01);the FBW,FI,and FE of 2000 mg/kg AAE group were lower than those of the control and CTC group on d 21(P<0.01).With the increase of AAE dose,the FBW and FE showed a quadratic elevation effect;FI showed a linear reduction effect on d 21(P<0.05).No significant difference was presented among groups in FBW,FI,and FE on d 42,and there was no significant dose-dependent e:ffect with the increase of AAE added(P>0.1).Part 2:Effects of AAE on the immune function of broilers and the molecular mechanism were explored by measuring the immune organ index and the content of immune indicators in serum,liver,spleen and small intestine,and the related gene expression.The results showed that the addition of 1500 mg/kg AAE to the diet significantly increased the thymus index of the broilers,and had a significant quadratic elevation effect with the increase of AAE dose on d 42(P<0.05).Serum immunoglobulins(Ig)M on d 21,and IgA,IgG,and interleukin(IL)-4 on d 42 and IgA,IgG,IgM,IL-2,and IL-4 content in the spleen on d 21 and 42 were higher at 1000 mg/kg AAE level than the control and CTC group(P<0.05).The content of IgA,IgG,IgM,IL-2,and IL-4 in the liver were higher at 1000-1500 mg/kg AAE level than the control on d 21 and 42(P<0.05).The content of IgG,IgM,slgA,IL-2,and IL-4 in the small intestine were higher at 1500 mg/kg AAE level than the control,but lower than CTC group on d 42(P<0.05).The content of IgA,IgG,IgM and IL-4 in serum on d 42,and the indicators of liver on d 21 and 42,spleen and small intestine on d 42 had a quadratic elevation effect(P<0.05).The content of IL-6 in serum on d 21,and the gene expression of IL-1β and nuclear factor kappa B(NF-κB)/p65 in the liver on d 42 at 500 and 1500 mg/kg AAE level were lower than the control(P<0.05).The gene expression of IL-1β and IL-6 in the liver were lower at 1000-2000 mg/kg AAE level than the control and CTC group on d 21(P<0.05).The content of IL-6 in the spleen on d 21 and 42,and IL-1β and IL-6 in the small intestine on d 21 were lower at 1500-2000 mg/kg AAE level than the control(P<0.05).The gene expression of IL-1β on d 21 and 42,and IL-6,NF-KB/p65 on d 42 in the spleen were lower at 500 mg/kg AAE level than the control(P<0.05).The gene expression of IL-1β and NF-KB/p65 in the small intestine were lower at 2000 mg/kg AAE level than the control on d 21(P<0.05).The content of IL-6 in serum and spleen on d 42,and the gene expression of IL-1 1β and IL-6 in the liver on d 21 had a linear reduction effect(P<0.05).The gene expression of IL-1β and NF-κB/p65 in the liver on d 42,and IL-1β on d 21 and 42,IL-6 and NF-κB/p65 in the spleen on d 42,and IL-1β,IL-6,and NF-κB/p65 in the small intestine on d 21 had a quadratic reduction effect with the increase of AAE dose(P<0.05).Part 3:Effects of AAE on the anti oxidative function of broilers and the molecular mechanism were explored by measuring the activities and content of antioxidant indicators in serum,liver,spleen and small intestine,and the gene expression of antioxidative enzymes in tissues.The results showed that serum activities of superoxide dismutase(SOD),glutathione peroxidase(GSH-Px)on d 21,and total antioxidant capacity(T-AOC)on d 42 were higher at 1500 mg/kg AAE level than the control(P<0.05).CAT and SOD gene expression in the small intestine were higher at 1000 mg/kg AAE level than the control(P<0.05).T-AOC,Catalase(CAT)and GSH-Px activity,and SOD gene expression on d 21 in the liver,T-AOC on d 42,GSH-Px activity and gene expression on d 21 in the spleen,and the activity of antioxidative enzymes in the small intestine on d 42 were higher at 1000-1500 mg/kg AAE level than the control(P<0.05).T-AOC,CAT and GSH-Px activity,and SOD gene expression in the liver,and T-AOC,SOD and GSH-Px activity and gene expression in the spleen on d 21,and small intestine enzyme activity on d 42 showed a quadratic elevation effect(P<0.05).CAT and SOD gene expression in the small intestine showed a linear elevation effect on d 21(P<0.05).The content of malondialdehyde(MDA)in the serum and spleen on d 42,and in the small intestine on d 21 and 42 were lower at 1000-1500 mg/kg AAE level than the control(P<0.05).The content of MDA in the serum on d 42,and in the small intestine on d 21 and 42 had a quadratic reduction effect with the increase of AAE dose(P<0.05).The content of MDA in the liver and spleen presented a linear reduction effect on d 42(P<0.05).In summary,the present results demonstrated that dietary AAE supplementation improved growth performance.Furthermore,AAE could affect the NF-κB signal pathway to regulate immune indicators and the related gene expression,resulting in improving immune function.Additionally,AAE could also increase the activity or content of antioxidant indicators and the related gene expression to improve antioxidant function of broilers.The optimal dose range of AAE in the diet of broilers was 1000-1500 mg/kg,which could bring a satisfactory effect as an alternative to antibiotics. |
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