Effects Of Dietary Addition Of Neolanmarckia Cadamba Extract On The Growth Performance,Immunity And Antioxidant Ability Of Micropterus Salmoides

The Neolanmarckia Cadamba is one of the important medicinal plants belonging to the Rubiaceae family.The main components of plants are triterpene glycosides flavonoids saponins indoles alkaloids.Katabine,etc.All these active ingredients have antibacterial properties and can inhibit the common pathogenic microorganisms in animal intestines,such as staphylococcus aureus escherichia coli and salmonella,etc.Therefore,they can be used as potential feeding antibiotic substitutes in animal feed.In order to explore the application value of Neolanmarckia Cadamba extract in aquaculture,In this paper,we first studied the minimal antibacterial activity of the extract of Neolanmarckia Cadamba against several common pathogenic bacteria in aquatic products.The experiment selected 480 healthy Micropterus salmoides fry with initial average weight(6.01g)and randomly divided them into 4 groups with 4 replicates in each group and 30 fishes in each replicate.T0 was set as the blank control group,T1 of the experimental group was added with 250 g of Neolanmarckia Cadamba extract,T2 of the experimental group was added with250 g of Neolanmarckia Cadamba extract and 200 g of ginseng polysaccharide,and the T3antibiotic group was added with 4 mg/kg of doxycycline hydrochloride.All groups were temporarily raised for 2 weeks followed by trail period of 60 days,in order to investigate the effects of the extract of Neolanmarckia Cadamba on the growth performance,serum biochemical index,antioxidant index and immune index of Micropterus salmoides.At the end of the experiment,aeromonas hydrophila was used to conduct the challenge test on the experimental fishes,and the infection model was established to explore the protection rate of the extract of Neolanmarckia Cadamba against the pathogenic Micropterus salmoides,so as to provide basic experimental data for its use as a new aquatic feed additives.The main research contents and results are as follows:1.To test the antibacterial activity of the extract of Neolanmarckia cadamba against four common pathogenic bacteria in aquatic products in vitro.The in vitro results showed that the extract of Neolanmarckia cadamba has antibacterial activity against Aeromonas hydrophila,Vibrio parahaemolyticus,Streptococcus agalactiae,Streptococcus iniae.The MIC values are:25,6.25,3.125 and 12.5(mg/m L),respectively.2.Effects of the addition of Neolanmarckia cadamba extract on the growth performance of Micropterus salmoides.compared with T0,T1 and T2 significantly increased the weight gain rate(P<0.05);Meanwhile,the specific growth rate of T2 group increased by 6.46%(P<0.05),feed coefficient significantly decreased(P<0.05),the hepatic body ratio decreased by 11.38%(P<0.05);There was no significant difference between the T0,T3 groups(P>0.05).The results showed that the dietary addition of 250 g of Neolanmarckia cadamba extract and200 g of Ginseng polysaccharides had the best effect on the weight gain rate of Micropterus salmoides,and could significantly reduce the feed coefficient(P<0.05).3.Effects on serum index of Micropterus salmoides.Compared with T0,glutamate transaminase in T1 and T2 groups had a downward trend,while glutamate transaminase had an upward trend;Total protein,albumin,total cholesterol and urea had no significant difference among groups(P>0.05);Triglycerides decreased in T1,T2 and T3 groups,with significant differences in T2 group(P<0.05).T-SOD,GSH-Px and T-AOC levels in serum of fish were significantly increased in T1 and T2 groups(P<0.05),there was no significant difference in T3 group(P<0.05);MDA content in T1 group decreased significantly by 48.38%(P<0.05),T2 decreased by 2.76%(P>0.05).In both T1 and T2 groups,the levels of IFN-γ,TNF-α,IL-1β,and IL-8 in fish serum were significantly increased(P<0.05),while the content of lg M and IL-10 were significantly reduced(P<0.05).The results indicated that the Neolanmarckia cadamba extract or with ginseng polysaccharide could significantly improve the antioxidant and specific immunity of fish,and the better results were obtained in the groups of 250 g of the extract of Neolanmarckia cadamba and 200 g of Ginseng polysaccharides.4.The effect of adding Neolanmarckia cadamba extract on the intestinal morphology of Micropterus salmoides.The height of intestinal villi in T1 group was significantly higher than that in T0 group and T2 group(P<0.05).The villi width and muscular layer thickness in the T2 group were significantly different from those in the T0 group(P<0.05),while T1constituted an upward trend,but the difference was not significant(P>0.05).The ratio of intestinal villi length to width in the T2 group was the lowest,which was significantly different from that in the T0 group(P<0.05).It was shown that Neolanmarckia cadamba extract or with Ginseng polysaccharides improve the intestinal and liver health of Micropterus salmoides.5.A model of bacterial infection in Micropterus salmoides was established by intraperitoneal injection of 0.5 m L of 2×10~7 CFU/m L Aeromonas hydrophila.The results showed that 10 hours after the challenge of Aeromonas hydrophila,the mortality rates in the T0,T1,T2,and T3 groups were 6.67%,0,3.33%,and 3.33%,respectively.24 hours after challenge,the mortality rates in the T0,T1,T2,and T3 groups were 46.67%,23.33%,40%,and 36.67%,respectively.36 hours after the challenge,the mortality rates in the T0,T1,T2,and T3 groups were 53.33%,36.67%,52.55%,and 56.67%,respectively.At the end of the experimental observation,the mortality rate in the T3 group exceeded that in the T0 group,and the mortality rate in the T1 group was the lowest.It was shown that the addition of the extract of Neolanmarckia cadamba to the feed can reduce the mortality of Micropterus salmoides after bacterial infection.Conclusively,this study shows that the extract of Neolanmarckia cadamba has antibacterial effect on the common aquatic pathogenic bacteria;adding the extract of Neolanmarckia cadamba extract to the feed of Micropterus salmoides enhances the growth performance,antioxidant and immunity of California sea bass,and it is also helpful to intestinal health as well.The extract of Neolanmarckia cadamba is a new potential additives in aquatic production.