Effects Of Yucca Schidigera Extract On Antioxidative And Immune Functions And Related Gene Expressions In Broilers

This study was carried out to explore the effects of dietary Yucca schidigera extract(YSE)on antioxidant and immune functions in broilers.A total of 128 15-day-old broiler chickens were randomly assigned to 4 treatments:maize-soybean meal as the basal control diet and the basal diet containing 100,200,or 300 mg/kg of YSE,respectively.Each treatment was consisted of 4 replicates with 8 broilers per pen(half male and half female).The experiment lasted 28 days and was divided into 2 stages of d 15?28 and d 29?42.The study was composed of 3 experiments:Experiment 1:Through measuring antioxidant enzyme activities in breast,liver,small intestine and serum samples,as well as the key antioxidant enzyme gene expressions in liver and small intestine,this part was designed to elucidate the effects of YSE on antioxidant functions in broilers.The results were showed as follows:On d 14,serum T-AOC and CAT activities were higher at 200 mg/kg YSE level(P=0.031,P=0.009);SOD concentration was stimulated at all 3 YSE treatments(P=0.014);200 rmg/kg YSE enhanced CAT activity and its gene expression in liver(P=0.035,P=0.003);T-AOC(P=0.039,P=0.031),GPx(P=0.016,P=0.045)and SOD(P=0.001,P=0.023)levels were enhanced at 100 mg/kg YSE level in duodenum and ileum;100 mg/kg YSE up-regulated SOD and GPx gene expression in ileum(P=0.018,P=0.003);CAT activity and its gene expression were improved at 100 mg/kg YSE level(P<0.001,P=0.028).On d 28,T-AOC activity in serum was improved at 200 and 300 YSE groups(P=0.006),but MDA concentration were decreased only at 300 mg/kg YSE dose(P=0.019);T-AOC activity was increased at 300 mg/kg YSE level in liver(P=0.001),liver GPx and SOD activities were improved at 300 mg/kg YSE level(P=0.002,P=0.049),GPx gene expression was up-regulated at 300 mg/kg dose in liver(P=0.028),liver MDA concentration was lowered at 300 mg/kg YSE dose(P=0.006);SOD level in duodenum was highest at 100 mg/kg YSE group(P=0.039);All YSE-added treatments enhanced GPx ability in ileum(P=0.022).300 mg/kg YSE addition improved T-AOC ability in breast(P=0.017).Experiment 2:Through measuring serum cytokine concentrations and antibody titres against Newcastle disease virus,this part proved the effectiveness of YSE on immune system in broilers.The results were showed as follows:On d 14,serum IL-6 concentrations were decreased at 200 and 300 mg/kg YSE level(P<0.001);On d 28,100 mg/kg YSE declined IL-4 level(P=0.002),enhanced IL-6 and IFN-? concentrations(P=0.004,P=0.026).Antibody titres against Newcastle disease was enhanced at 100 mg/kg YSE group in both experimental period(P<0.001,P=0.032).Experiment 3:Through measuring serum nitric oxide(NO)concentrations and inducible nitric oxide synthase(iNOS)activity,and tissue gene expression of iNOS,this part was carried out to test the effects of YSE on NO pathway in broilers.The results indicated that on d 14,serum NO concentration and iNOS level were enhanced at 100 mg/kg YSE level(P=0.032,P=0.048),and iNOS gene expression was up-regulated at 200 mg/kg YSE level(P=0.031),in addition,there were increasing tendencies of iNOS expression in liver and spleen at 100 mg/kg YSE dose(P=0.081,P=0.075);On d 28,NO concentrations and iNOS activity in serum,and tissue iNOS gene expression were not different among all treatments.The results showed that dietary YSE could exhibit positive effects on antioxidant and immune functions in broilers.Different YSE dosage could stimulate antioxidant abilities in broilers through improving different tissue antioxidant functions;In terms of immune function,100 mg/kg YSE exhibited highest immune-enhancing ability in broilers;100 mg/kg YSE could stimulate immune and antioxidant functions by enhancing serum NO and iNOS concentrations in broilers.