| In this paper,two experiments were conducted to evaluate the antibacterial effects of individual plant extracts and their compounds on chicken pathogenic bacteria [Escherichia coli(E.coli)and Salmonella] in vitro and the bioavailabilities of individual plant extracts and their compounds with stronger antibacterial activities for broilers.Experiment 1: Study on the in vitro antibacterial effets of plant extracts and their compounds against the chicken pathogenic bacteria.Two trials in the first experiment were divided.In trial 1: 11 treatments [thyme oil,oregano essential oil,cinnamon essential oil,garlic oil allicin,skullcapflavone,bamboo leaf flavonoids,astragalus polysaccharides,berberine,matrine,chlorogenic acid and chlortetracycline(the positive control)] were arranged,and all treatments were replicated 6 times.The inhibition zone diameters of plant extracts against E.coli and Salmonella were determined by Oxford cup method.In trial 2: According to the results of trial 1,three kinds of plant extracts(cinnamon essential oil,matrine and chlorogenic acid)with the strongest inhibitory effects on the E.coli were screened out and compouded in different concentration ratio respectively.The inhibition zone diameters of plant extract compounds against E.coli were determined by Oxford cup method.At the same time,the control treatments of the three plant extracts at corresponding concentrations were arranged.Therefore,there were 20 treatments in total,and all treatments were replicated 6 times.Similar to this,3 kinds of plant extracts(bamboo leaf flavonoids,skullcapflavone and cinnamon essential oil)with the strongest inhibitory effects on the Salmonella were screened out and compounded,and the inhibition zone diameters of the plant extract compounds and the controls against Salmonella were determined by Oxford cup method.Then,all the 17 treatments were replicated 6 times.According to the above results,the antibacterial effect of the compounds of bamboo leaf flavonoids and cinnamon oil at different concentration ratios against Salmonella were determined,and the best proportion in combination was selected.And all the 15 treatments were replicated 6 times.The results showed that five plant extracts had the bacteriostatic activities against E.coli,and the order of their antibacterial activities from high to low was: cinnamon essential oil > matrine > chlorogenic acid > thyme essential oil > oregano essential oil.In addition,eight plant extracts had the bacteriostatic activities against Salmonella,and the order of their antibacterial abilities was as follows: bamboo leaf flavonoids > skullcapflavone> cinnamon essential oil > matrine > chlorogenic acid > oregano essential oil > thyme oil > allicin.Compared with the control,the compounds of cinnamon essential oil,matrine and chlorogenic acid could not significantly improve the antibacterial activities against E.coli(P> 0.10).However,the combination of bamboo leaf flavonoids and cinnamon essential oil could significantly improve the antibacterial activities against Salmonella(P <0.0001),and the antimicrobial effect was the highest at the concentration ratio of 25: 150(1: 6)(P <0.044).Among the 10 plant extracts,three plant extracts with the best bacteriostatic effects against E.coli were cinnamon essential oil,matrine and chlorogenic acid,and the 3 plant extracts with best bacteriostatic effects against Salmonella were bamboo leaf flavonoids,akullcapflavone and cinnamon essential oil.The combination of bamboo leaf flavonoids and cinnamon essential oil could improve the bacteriostasis against Salmonella,and the antimicrobial effect was the highest at the concentration ratio of 1: 6.Experiment 2: Study on the bioavailabilities of plant extracts and their compound for broilers.According to the results of experiment 1,the cinnamon essential oil and compound of bamboo leaf flavonoids and cinnamon essential oil(1:6),which had the best bacteriostatic effect on E.coli and Salmonella,respectively,were added to broilers' diets.A total of 576 1-day old Arbor Acres(AA)commercial broilers were randomly allotted to 9 treatments for 8 replicates of 8 birds each,in a completely randomized design,and fed a basal corn-soybean meal diet as control(without plant extracts and antibiotic)and the basal diet supplemented with 50 mg/kg aureomycin,50,100,200,400,or 800 mg/kg of cinnamon essential oil,16.7 mg/kg bamboo leaf flavonoids + 100 mg/kg cinnamon essential oil(bamboo leaf flavonoids: cinnamon essential oil=1:6),33.3 mg/kg bamboo leaf flavonoids + 200 mg/kg cinnamon essential oil(bamboo leaf flavonoids: cinnamon essential oil=1:6)for 42 days.The results showed:(1)The addition of cinnamon oil and compound of cinnamon oil and bamboo leaf flavonoids had no effect(P> 0.169)on the growth performance during the 1-21 and 22-42 days,carcass traits and meat quality on d 42,IgG,serum IgA and IgM contents in on d 21,plama IgG and IgA on d 42,and T lymphocyte transformation rate in blood on d 21 and 42,but did influence(P<0.021)IgM contents in serum on d 42.Broilers from the treatment on 800 mg/kg cinnamon essential oil or compound of cinnamon essential oil and bamboo leaf flavonoids(200+33.3 mg/kg)had higher(P<0.039)IgM content in serum than those from the control treatment.(2)The addition of cinnamon oil and compound of cinnamon oil and bamboo leaf flavonoids had no effect(P> 0.094)on the malondialdehyde(MDA)content and total antioxidant capacity(T-AOC)in the serum and T-AOC content in the liver on d 21,MDA contents and T-AOC in the serum and liver on d 42,but affected(P<0.048)the MDA content in liver on d 21.The addition of 100 mg/kg cinnamon essential oil decreased(P<0.042)MDA cotent in liver on d 21.(3)The addition of cinnamon oil and compound of cinnamon oil and bamboo leaf flavonoids did not affect(P> 0.19)the caecal E.coli contents on d 21,caecal Lactobacillus contents on d 42,and ileal Lactobacillus contents on d 21 and 42,but affected caecal Lactobacillus on d 21,and caecal E.coli and Bifidobacterium contents on d 42(P<0.0056).Among all the treatments,the additon of cinnamon essential oil at 100 mg/kg had the best effect on the increase of Lactobacillus proportion in the cecum on d 21 and Bifidobacterium proportion in the cecum on d 42,and the decrease of E.coli proportion in the cecum on d 42.In conclusion,cinnamon oil supplementation improved the immune function,antioxidant capacity and intestinal microflora,and the addition of the compound of cinnamon essential oil and bamboo leaf flavonoids also enhanced the immune function and intestinal microflora,but the effect of the compound was not better than that of single cinnamon oil.The results of this study showed that,to some degree,antibiotics could be replaced with 100 mg / kg of cinnamon essential oil in the diets of broilers.These results were of great theoretical and practical significance for reducing the use of antibiotics in broiler's diet and its risk to the environment and human health. |
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