Effects Of Adding Clostridium Butyricum To Low Fish Meal Feed On The Growth,Digestive Physiology,Intestinal Immunity And Flora Of Triploid Rainbow Trout

Clostridium butyricum is a kind of probiotics.It has a beneficial effect on the body.This experiment mainly studied the effects of growth,digestive physiology,and intestinal health on triploid rainbow trout when adding C.butyricum to the diet.It mainly includes three parts.1.Effects of C.butyricum on the growth performance and digestive physiology of triploid rainbow troutA total of 450 triploid rainbow trout fed isonitrogenous and isoenergetic diet supplemented with different levels of C.butyricum(0,1×10⁶,1×10⁷,1×10⁸,1×10⁹CFU g^-1)for 8 weeks.The results showed that the weight gain rate and specific growth rate of rainbow trout were significantly increased in the G4 group（P<0.05）.Besides,the G4 group had the lowest feed conversion ratio.There were no significant differences in the viscerosomatic index and survival rate of rainbow trout（P>0.05）.It also had no significant effect on the body moisture,ash,and crude lipid among the groups（P>0.05）,but the crude protein content increased,and the highest value was shown in the G5 group（P<0.05）.The activities of lipase,trypsin increased first and then decreased with the increase of dietary C.butyricum level,and the highest value was shown in the G4 group（P<0.05）.However,the activities ofα-amylase decreased significantly（P<0.05）.2.Effects of C.butyricum on physiological,biochemical,and immune indexes of triploid rainbow troutThere were significant effects of C.butyricum on the antioxidant and immune performance of rainbow trout.The results showed that the activities of superoxide dismutase（SOD）,catalase（CAT）contents in serum of rainbow trout were increased first and then decreased.The activities of malonaldehyde（MDA）were significantly decreased（P<0.05）.The contents of SOD and CAT in liver increased with dietary C.butyricum supplementation,but the activities of MDA were significantly decreased（P<0.05）.The activities of lysozyme（LZM）and immunoglobulin（Ig M）contents in the serum of rainbow trout were significantly increased（P<0.05）.C.butyricum had a significant effect on the expression of genes related to the intestinal immunity of rainbow trout（P<0.05）.The maximum gene expression of IL-1βwas shown in the G3group.With the increase of the C.butyricum addition level,the gene expressions of IL-8,IL-10,NF-κB,My D88 and Zonula occludens-1 increased,but the gene expression of TNF-αdecreased and Occludin was no significant difference among the groups.The gene expression of IL-2 decreased gradually,but there was no significant difference among the groups（P>0.05）.3.Effects of C.butyricum on the intestinal microbial diversity of triploid rainbow troutThe effects of different concentrations of C.butyricum on the structure and diversity of the intestinal microbe of rainbow trout were studied by the method of high-throughput sequencing（Illumina Mi Seq）technology.The results showed that 30samples of rainbow trout intestinal contents were obtained 1,416,048 valid sequences and 312 operational taxonomic units.The Alpha diversity analysis showed that there was no significant difference in the Chao1 index,ACE index,Shannon index,and Simpson index between the 5 experimental groups（P>0.05）.The Beta diversity analysis showed that the structure of the flora among the groups was similar.The dominant populations were Proteobacteria,Firmicutes,Actinobacteria,and Cyanobacteria.With the increase of dietary C.butyricum levels,the abundance of Proteobacteria increased first and then decreased,the abundance of Firmicutes and Actinobacteria decreased first and then increased,while the abundance of cyanobacteria in the experimental group was lower than that in the control group.The main bacterial genera are Burkholderia,Pseudomonas,Rhodococcus,Bacillus flora.Clostridium butyricum will affect the changes in the structure of the intestinal flora of rainbow trout,the proportion of the flora varies under different concentrations.the abundance of Burkholderia increased in G4 and G5 groups.There was little difference in flora between Pseudomonas and Rhodococcus.The proportion of Bacillus in G3,G4 and G5 groups is higher than that in G1 and G2 groups.Conclusion:To sum up,it has a good effect when adding 1×10⁸ CFU g^-1 Clostridium butyricum to the low fish meal（15%）feed.Clostridium butyricum promotes the growth of rainbow trout by enhancing the body’s antioxidant,immune capabilities and affecting the intestinal flora.It can also increase the feed utilization,thereby improving the health of the body.