| With the decline of fishery resources and the rapid development of the aquaculture industry,the contradiction between supply and demand of fish meal has intensified,Finding a suitable source of fish meal replacement protein is a hot issue in the aquaculture industry.Soybean meal is an ideal source of fish meal replacement protein.However,a high proportion of soybean meal substitute feed fish meal will destroy the intestinal structure,induce intestinal inflammation and affect fish growth.In this paper,Nibea albiflora was used as the research object to study the effects of adding high proportion of soybean meal to replace fish meal and adding tributyrin(TB)on the growth,intestinal structure and intestinal health of Nibea albiflora.Six groups of feeds were designed: 42% fish meal content was used as the positive control group(FM group),and soybean meal replaced 40%fish meal.The protein group was negative control group(SBM group),then 0.05%,0.1%,0.2%,0.4% tributyrin was added as the experimental group on the basis of SBM group(TB0.05 group,TB0.1 group,TB0.2 group,TB0.4 group).Initial fish body weight(9.00±0.05g),cultured for 8 weeks.The specific experimental content and results are as follows:1.Effect of tributyrin on growth index and body composition of Nibea albifloraThe results showed that there was no significant difference in survival rate(SR)between the groups(P>0.05).The terminal body weight(FBW),weight gain rate(WGR),specific growth rate(SGR)and feed efficiency(FER)of the FM group were significantly higher than those of the SBM group(P<0.05).The FBW,WGR,SGR and FER of TB0.1group were significantly higher than that of SBM group(P<0.05),and there was no significant difference with FM group(P>0.05).With the increase of the addition level of tributyrin,the food intake of the Nibea albiflora showed a downward trend,and the food intake of the TB0.4 group was significantly lower than that of the SBM group and the TB0.05 group(P<0.05).With the increase of the addition level of tributyrin,the feed efficiency of Nibea albiflora increased first and then decreased.The TB0.1 group was significantly higher than the SBM group(P<0.05),and there was no significant difference between the two groups(P>0.05).Therefore,under the condition that soybean meal replaced 40% fish meal protein,the addition of 0.1% tributyrin was the best.Subsequent experiments mainly analyzed FM group(FM),SBM group(SBM)and TB0.1 group.The results showed that there was no significant difference in crude protein,crude ash and water content between the groups(P>0.05),but the crude fat content in SBM group and TB0.1 group was significantly lower than that in FM group(P<0.05).There were no significant differences in the values ?of n-6 PUFA,?n-3 PUFA,?n-3 LC-PUFA between the muscles of the scorpion fish in each group(P>0.05),and the ?n-3/n-6PUFA in the FM group was significantly higher.In the SBM group and the TB0.1 group(P<0.05).The histidine(His)and arginine(Arg)in theTB0.1 group were significantly higher than those in the SBM group,and there was no significant difference from the FM group.2.Effects of tributyrin on the intestinal structure of the Nibea albifloraThe results showed that the height of intestinal folds in the FM group and the TB0.1group was significantly higher than that in the SBM group(P<0.05),but there was no significant difference between the FM group and the TB0.1 group(P>0.05).There was no significant difference in the thickness of the muscle layer of the three groups of feed-treated squid(P>0.05).The ratio of villous circumference in the FM group was significantly higher than that in the SBM group(P<0.05).There was no significant difference between the TB0.1 group and the other two groups(P<0.05).The intestinal microvilli height in the FM group was significantly higher than that in the SBM group and the TB0.1 group(P<0.05),and the TB0.1 group was significantly higher than the SBM group(P<0.05).The intestinal microvilli density of the FM group was significantly higher than that of the SBM group and the TB0.1 group(P<0.05),and the TB0.1 group was significantly higher than the SBM group(P<0.05).At the end of the experiment,the expression of gut structure-related genes was studied in the distal intestine of the Nibea albiflora.The expression of Claudin3,Claudin4 and ZO1 in the SBM group was significantly lower than that in the FM group(P<0.05).The expression levels of Occludin,JAM1,and MUC2 were also lower than those in the FM group(P>0.05).The addition of TB increased the expression of tight junction-associated genes in the SBM group,and the expression levels of Claudin3,Claudin4,JAM1,and ZO1 were significantly higher than those in the SBM group(P<0.05).3.Effects of tributyrin on the intestinal structure of the Nibea albifloraAt the end of the experiment,the expression of immune-related genes was studied in the distal intestine of the Nibea albiflora.The expression of TNF?,IL1? and SOCS3 in the SBM group was significantly higher than that in the FM group(P<0.05).The expression level of IL1? in TB0.1 group was significantly lower than that in SBM group(P<0.05).The fecal microbial analysis of the distal intestine of the Nibea albiflora was carried out 6 h after the meal.The Observed species and Chao1 index of the SBM group were significantly lower than those of the FM group and the TB0.1 group(P<0.05).This indicates that SBM has significantly reduced intestinal microbial species after replacing fish meal,but TB can improve this condition.The PCoA results showed that the FM group and the TB0.1 group were similar in location,and the SBM group was more dispersed.At the level of the phylum,the dominant intestinal flora of each group of Nibea albiflora is Proteobacteria,Firmicutes,Actinobacteria,Cyanobacteria,Bacteroidetes,and Acidobacteria.The abundance of actinomycetes and acid bacteria in the FM group and the TB0.1 group was significantly higher than that in the SBM group(P<0.05).At the level of the class,the dominant intestinal flora of each group of scutellariae is Alphaproteobacteria,Betaproteobacteria,and Gammaproteobacteria.The?-proteobacteria of the FM group were significantly higher than the SBM group and the TB0.1 group(P<0.05),and the?-proteobacteria of the TB0.1 group were significantly higher than the SBM group(P<0.05).The?-proteobacteria of the FM group and the TB0.1 group were significantly lower than the SBM group(P<0.05).At the genus level,Pathogenic genus Acinetobacter was significantly lower in the TB0.1 group than in the SBM group(P<0.05),and was not significantly different from the FM group(P>0.05).TB0.1 group of bacteria that can degrade organic matter(Hydrogenophaga,Sphingopyxis,Devosia,Rhodocyclaceae,and Methyloversatilis)was significantly higher than the SBM group(P<0.05),and was not significantly different from the FM group(P>0.05).Tributyric acid glyceride enriches the diversity of intestinal flora,reduces the abundance of pathogenic bacteria,enhances the abundance of functional organic bacteria,and improves intestinal health. |
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