Effects Of Clostridium Butyricum On The Growth,Nutrition Utilization And Intestinal Health Of The Symphysodon Haraldi

The Symphysodon haraldi is a rare species of ornamental fish and is known as the"king of tropical ornamental fish".As a carnivorous fish,Symphysodon haraldi farming is generally based on moist bait made of fresh beef heart and shrimp meat,which is called"beef heart burger".Although this kind of bait is widely used in aquaculture,its nutrients do not necessarily meet the nutritional needs of the Symphysodon haraldi.The bait is frozen and rich in high protein,so it is easy to produce residual bait in the process of being bitten by the Symphysodon haraldi,affect water quality Clostridium butyricum belongs to the genus Clostridium,which can produce digestive enzymes,short-chain fatty acids and various nutrients,enhance immunity and antioxidant capacity,and regulate the balance of intestinal flora in the body.The mechanisms by which utilization and gut health are affected are not fully understood.Therefore,after domestication of the same batch of colorful angelfish for 2 weeks,180 individuals with similar body shapes(initial body weight 2.03±0.4 g,initial body length 3.39±0.26 cm,initial body height 2.90±0.12 cm)were selected as the research objects and randomly divided into6 sets.Clostridium butyricum 0(control,NC),1×10~4(C1),1×10~5(C2),1×10~6(C3),1×10~7(C4),1×10~8(C5)cfu/g of bait,the breeding cycle is 8 weeks.After the test,the related indicators of growth and body,the whole fish body composition index,the nutrient digestion index,the liver enzyme activity index,the intestinal tissue morphology observation,the intestinal p H value,the intestinal enzyme activity index,the short chain were detected respectively.Fatty acid content and intestinal flora structure,and the correlation analysis between short-chain fatty acid content and intestinal flora and the prediction analysis of intestinal flora function were carried out to explore the effect of Clostridium butyricum on the growth and nutrient utilization of colorful Symphysodon haraldi,the influence of intestinal health,provide scientific basis for the application of Clostridium butyricum in aquatic feed and the optimum addition amount in Symphysodon haraldi bait.The test results were as follows:(1)Effects of Clostridium Butyricum on growth,body composition and nutrient utilization of Symphysodon haraldiAfter 8 weeks of breeding experiments,the 1×10~5 cfu/g group had the highest weight gain rate and specific growth rate,and the lowest feed coefficient.In terms of body composition,the crude protein content of the 1×10~5 cfu/g and 1×10~7 cfu/g groups increased significantly(P<0.05),and the protein digestibility of the 1×10~5 cfu/g group were significantly higher(P<0.05).(2)Effects of Clostridium Butyricum on intestinal morphology and enzyme activity of various organs in Symphysodon haraldiCompared with the control group,the addition of 1×10~5 cfu/g,1×10~6 cfu/g Clostridium butyricum to the diet significantly increased the villus height of the midgut,increased the villi-crypt ratio(P<0.05)and it was found by staining that intestinal acid mucopolysaccharides were more secreted in the 1×10~5 cfu/g group.Compared with the control group,after the addition of Clostridium butyricum to the diet,the intestinal trypsin activity and liver superoxide dismutase activity in the 1×10~5 cfu/g group and the liver catalase activity in the 1×10~7 cfu/g group were significantly increased.The intestinal malondialdehyde content in the 1×10~6 cfu/g group was significantly lower than that in the control group(P<0.05).(3)Effects of Clostridium butyricum on the intestinal flora and content of short-chain fatty acids in the Symphysodon haraldiCompared with the control group,the addition of Clostridium butyricum to the diet significantly increased the secretion of short-chain fatty acids(P<0.05).There were no significant differences in species richness(Sobs,Ace,and Chao1)and diversity(Shannon and Simpson)among all experimental groups(P>0.05),but the proportion of gut microbiota changed.At the phylum level,the 1×10~5 cfu/g group had the highest abundance of Firmicutes and was significantly higher than that of the 1×10~4 cfu/g group.Compared with the control group,the Bacteroidetes in 1×10~5 cfu/g and 1×10~7 cfu/g groups were significantly increased,and the Desulfobacteria in 1×10~4 cfu/g and 1×10~5cfu/g groups were significantly decreased(P<0.05).At the genus level,compared with the control group,the proportion of Desulfovibrio in the 1×10~4 cfu/g,1×10~5 cfu/g and1×10~7 cfu/g groups was significantly lower(P<0.05).PCo A and NMDS analysis showed that although there were differences in the structure of gut microbiota between groups,the differences were homologous.Correlation analysis showed that acetate was positively correlated with Bacteroides and Parabacteria,and isobutyric acid was positively correlated with Bacteroidetes(P<0.05).Clostridium butyricum promotes healthy growth of Symphysodon haraldi by regulating gut microbe-mediated functions such as improving nutrient digestion and absorption and immunity.In summary,adding an appropriate amount of Clostridium butyricum can enhance the intestinal barrier function of the colorful Symphysodon haraldi,improve digestion and antioxidant capacity,increase nutrient utilization and short-chain fatty acid content,regulate the structure of intestinal flora,and maintain intestinal health.Under the conditions of this experiment,adding 1×10~5 cfu/g Clostridium butyricum to the bait of Symphysodon haraldi had the best effect.