| In this study,Eucommia ulmoides Oliver bark aqueous extract at different concentrations were added to rainbow trout basic feed to explored its effects on rainbow trout intestinal microbiota structure,intestinal histology and genes expression of Toll-like receptor families and genes expression of Toll-like receptor signaling pathway-related,the research results enriched the basic data of rainbow trout immunostimulant.The main research results and conclusions are as follows:1.Effects of Eucommia ulmoides Oliver bark aqueous extract on intestinal microbiota structure and diversity of rainbow trout.The experimental juvenile rainbow trout with an average body weight of(145.56±4.12)g were randomly divided into 5 groups with 3 replicates per group and30 fish per replicate.Fish in the 5 groups were fed the basal diets supplemented with Eucommia ulmoides Oliver bark aqueous extract at the concentrations of 0(control group),0.5%,1.0%,2.0% and 4.0%,respectively.The experiment lasted for 10 weeks.The results showed that:(1)The Simpson index of the 2% and 4% groups was significantly higher than that of the 0.5% and 1% groups(P < 0.05),but there was no significant differences compared with the control group(P > 0.05).The Shannon index of the 1% group was significantly higher than that of the 2% and 4.0% groups(P< 0.05),but no significant differences compared with the control group and 0.5%group(P > 0.05).(2)At the phylum level,the dominant bacterial communities was Tenericutes,Firmicutes,Fusobacteria,and Proteobacteria.(3)Compared with the control group,the abundances of harmful bacterial communities were decreased most significantly in the 2% group.In the 4% group,Excepted for the Brucellaceae,Sphingomonadaceae and Ochrobactrum species,the abundances of the 4% group were decreased significantly(P < 0.05).(4)Compared with the control group,the abundances of Bradyrhizobiaceae and Comamonadaceae in beneficial bacterial communities of 4.0% groups were significantly increased(P < 0.05).In conclusion,itwas suggested that added 4% Eucommia ulmoides Oliver bark aqueous extract in rainbow trout feed to improved the intestinal microbiota structure of rainbow trout.2.Effects of Eucommia ulmoides Oliver bark aqueous extract on rainbow trout intestinal histology.The results showed that: The intestinal mucosal fold structure was completed,tunica propria and muscularis structure was completed among all groups,Among them,the intestinal microvillu in the 4% group and the control group were neatly arranged,but the intestinal microvillu in the 0.5% group,1% group,and 2% group were not arranged neatly.The number of goblet cells in the 4% group and the control group was not significantly increased or decreased,but The number of goblet cells in0.5% group,1% group and 2% group were significantly increased.In conclusion: The Eucommia ulmoides Oliver bark aqueous extract in the feed has not obviously effects on the intestinal mucosal fold structure,tunica propria and muscularis structure of rainbow trout,but the 0.5%,1% and 2% groups had an increased number of goblet cells,and some intestinal microvillu were unevenly arranged.3.Effects of Eucommia ulmoides Oliver bark aqueous extract on Toll-like receptor families genes expression of rainbow trout.The results showed that:(1)There were no significant differences in intestinal TLR1 gene mRNA expression between the 1% and 4% groups(P > 0.05),but both were significantly higher than the control group(P < 0.05).(2)The intestinal TLR3 gene mRNA expression in the 4% group was significantly higher than that in the control group and the 1% group(P < 0.05).(3)The expression of TLR5 gene mRNA in the control group was significantly higher than that in the 1% and 4% groups(P <0.05).(4)The TLR2,TLR4,TLR5 m,TLR7,TLR9,TLR19 and TLR22 genes m RNA expression levels were not significantly differences among all groups(P > 0.05).In conclusion: The 4% Eucommia ulmoides Oliver bark aqueous extract can significantly up-regulated TLR1 and TLR3 genes m RNA expression,significantly down-regulated TLR5 gene mRNA expression.4.Effects of Eucommia ulmoides Oliver bark aqueous extract on Toll-like receptor signaling pathway-related genes of rainbow trout.The results showed that:(1)There was no significant differences in intestinal IL-6,IL-12 and MyD88 genes mRNA expression in the 1% and 4% groups(P > 0.05),but they were significantly higher than those in the control group(P < 0.05).(2)There was no significant differences in the mRNA expression of CD40,TNF?,NF-?Bie,NF-?Bid,IRAK4,IL-8 and IL-1? genes groups(P > 0.05).In conclusion: Adding 1%and 4% of Eucommia ulmoides Oliver bark aqueous extract to feed could significantly up-regulated the expression of IL-6,IL-12 and MyD88 genes mRNA in intestinal toll-like receptor signaling pathway in rainbow trout,and play an immune regulatory role through the toll-like receptor signaling pathway.In conclusion,adding 4% Eucommia ulmoides Oliver bark aqueous extract to rainbow trout feed can effectively improve the intestinal microbiota structure,and regulated the relative expression of TLRs/MyD88/NF-?B signaling pathway related genes to regulated the rainbow trout intestinal health. |
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