| This study was conducted to investigate the effects of Ginkgo biloba leaves(Ginkgoaceae,Ginkgo biloba)and Ginkgo biloba extract(EGB)on growth mechanism of broilers by two experiments.Firstly,the optimum supplementation levels of Ginkgo leaf or EGB in the diet were determined according to the the nutrient and energy utilization of broilers;Then,through the growth performance,antioxidant and immune function,the mechanism of Ginkgo leaf and EGB was replaced of antibiotics was proved.It provides theoretical basis for the application of Ginkgo leaf and EGB in broiler industry.Exp.1 Effect of different concentration gradient of Ginkgo leaf and EGB on nutrient and energy utilization of broilers.Experiment using two hundred and fourty 21-d-old male Arbor Acres(AA)broilers that were randomly allocated to 15 treatments with 8 replicates in a complete randomized design.The dietary treatments were corn-soybean meal based diets: T1,positive,control diet + 0.002% Bacitracin;Broilers in T2,T3 and T4 groups were fed the positive diet supplemented with 2%,4% and 6% Ginkgo leaves,respectively,and broilers in T5,T6 and T7 groups were fed the positive diet supplemented with 0.04%,0.08% and 0.12%EGB,respectively.T8,negative,control diet(no antibiotics);Broilers in T9,T10 and T11 groups were fed the negative diet supplemented with 2%,4% and 6% Ginkgo leaves,respectively,and broilers in T12,T13 and T14 groups were fed the negative diet supplemented with 0.04%,0.08% and 0.12%EGB,respectively.And T15,the endogenous treatment was fed the negative control diet,and analyzed the true utilization of broilers.The diets were made as wheat bran was replaced with Ginkgo leaves.The total fecal urine method was used and the adaptation period was 7 days and the trail period was 3 days.The result of this experiment indicated that supplementation of Ginkgo leaf,EGB and Bacitracin increased(P < 0.05)the apparent digestibility(AD)and true digestibility(TD)of EE compared with those of control treatment.As compared with control treatment,supplementation of Ginkgo leaf and EGB increased(P < 0.05)the AD and TD of EE with antibiotics,and the utilization of CP was increased(P < 0.05)in EGB supplemented treatments.Regardless of Bacitracin,as the levels of Ginkgo leaf and EGB increased in the diet,the AD and TD of EE were linearly and quadratically(P < 0.05)increased compared with those of control treatments,and the AD and TD of CP were linearly(P < 0.05)increased in Ginkgo leaf supplemented treatments.There was a significant interaction(P < 0.05)between Ginkgo leaf and Bacitracin or EGB and Bacitracin supplementation in the diets for the utilization of AMEn and TMEn compared with those of control treatments.Regardless of Bacitracin,the AD and TD of Thr、Val、Ile、Leu、Phe、His、Arg and TEAA(utilization of EAA except Trp)were quadratically(P < 0.05)increased,and the AD and TD of Lys and Met were also quadratically(P < 0.05)increased in EGB-supplemented groups compared with those of control treatments.Exp.2 Effect of Ginkgo biloba leaves and EGB on growth performance,antioxidant and immune function of broilersSix hundred and forty 1-day-old male Arbor Acres broilers were randomly allocated to 4 treatments with 8 replicates of 20 broilers in a single factor complete randomized design.Broilers in control groups were fed a corn-soybean meal type basal diet,and broilers in experiment groups were fed the basal diet supplemented with 6% Ginkgo leaves,0.08% EGB and 0.002% Bacitracin,respectively,and Ginkgo leaves replacing equivalent bran in the basal diet.The experiment lasted for 42 d,and the broilers were fed a starter diet from d 1 to d 21 and a grower diet from d 22 to d 42.The result of this experiment indicated that supplementation of Ginkgo leaf,EGB and Bacitracin significantly increased(P < 0.05)the body weight at 21 days of age and 1 to 42 days of average daily feed intake compared with the control group.The activity of glutathione peroxidase in serum and liver of broilers at 21 and 42 days of age in experiment groups were significantly increased(P < 0.05)compared with the control treatment.Compared with control group,supplementation of Ginkgo leaves and EGB increased(P < 0.05)the serum total protein(TP)of broilers at 21 days of age,while there were significantly decreased(P < 0.05)the triglyceride(TG)and total cholesterin(TCHO)at 21 and 42 days of age.Supplementation of Ginkgo leaf and EGB significantly increased(P < 0.05)the spleen index at 21 days of age compared with those bacitracin groups.The bursa of fabricus index at 21 days of age,the spleen index and thymus index at 42 days of age were increased(P < 0.05)in EGB-supplemented treatments compared with other groups.Compared with control group,supplementation of Ginkgo leaves and EGB increased(P < 0.05)the lymphocyte proliferation at 21 and 42 days of age.Compared with control and bacitracin groups,supplementation of Ginkgo leaves and EGB in the diet increased(P < 0.05)IgA at 21 days of age and IgM at 42 days of age of broilers.Supplementation of Ginkgo leaf,EGB and Bacitracin significantly increased(P < 0.05)TNF-α at 21 days of age and IFN-γ and TNF-α at 42 days of age of broilers compared with those the control treatment.Compared with control treatment,supplementation of Ginkgo leaves and EGB increased(P < 0.05)the half chamber rate and eviscerated rate of broilers,and the half chamber rate,eviscerated rate and breast rate were significantly increased(P < 0.05)in EGB-supplemented groups compared with those of Ginkgo leaf supplemented treatments.In conclusion,supplementation of Ginkgo leaf and EGB improved the nutrient and energy utilization,growth performance,antioxidant and immune function of broiler chickens in a dose-dependent manner,and the optimum supplementation levels of Ginkgo leaf or EGB in the diet of broilers was 6% or 0.08% of diet;moreover,it appeared that under the same concentrations of the active substances in Ginkgo leaf and EGB,supplementation of EGB had a better effect than those in Ginkgo leaf-supplemented treatments. |
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