| In this work,the growth performance,serum biochemical indicators,antioxidant and immune indicators,digestive enzyme activity,liver and intestine structure and intestinal flora of Micropterus salmoides feed on the bacterium enzyme synergistic fermented soybean meal in the place of different proportions of fish meal were studied,and the major results for this work are below.1.Effect of bacterium enzyme synergistic fermented soybean meal on growth performance and tissue biochemical indexes of M.salmoides.In the test,450 M.salmoides with an initial weight of 5.08 ± 0.01 g were divided into6 groups randomly.They were fed with basal feed,bacterium enzyme synergistic fermented soybean meal in the palce of 10%,20%,30%,40% fish meal and replaced feed for 30%fish meal replaced by ordinary soybean meal,and marked as T0,T10,T20,T30,T40,NC30 respectively.The experiment were applied in an indoor circulating water system for 57 days.After the feeding period,the growth performance index was weighed to calculate the body composition of the whole fish,and blood samples were collected for analysis of serum biochemical indexesThe results showed that except for the T10 group,the specific growth rate,protein efficiency,and protein deposition rate of M.salmoides in each replaced group were significantly lower than those in T0 group(P < 0.05),while the feed coefficient was significantly higher than that in the T0 group(P<0.05).Compared with the T0 group,the weight gain rate of M.salmoides in the T40 and NC30 groups was reduced significantly(P< 0.05),and the survival rate of M.salmoides in the NC30 group was decreased significantly(P<0.05).The replacement of fish meal with bacterium enzyme synergistic fermented soybean meal affected the physical indicators,body components,lipid metabolism index and immune anti-oxidation ability of M.salmoides significantly(P <0.05).The results reveal that the bacterium enzyme synergistic fermented soybean meal could increase the activity of serum aspartate aminotransferase and superoxide dismutase signicicantly,while there is no effects on the survival rate of M.salmoides.The weight and weight gain rate would decreased significantly when the substitution rate was higher than30%.2.Effect of bacterium enzyme synergistic fermented soybean meal on digestive enzyme activity and tissue structure of M.salmoides.The digestive enzyme activities in the stomach,foregut,liver of M.salmoides were analysied and the structure of midgut,liver were observed by paraffin sections and HE staining after the feeding period.The results showed that the replacement of bacterium enzyme synergistic fermented soybean meal could increased foregut trypsin and lipase activity significantly(P<0.05),and reduced gastric lipase activity significantly(P<0.05),but without significant effect on pepsin,gastric amylase,foregut amylase,and liver lipase activities of M.salmoides(P>0.05),except for the T20 group,there was no significant difference on liver protease and liver amylase activity in each group(P>0.05).The height of the midgut villi and the thickness of the myometrium of M.salmoides decreased with the increasement of the fish meal replaced proportion.The height of midgut villi in T10 group was significantly higher than that in T30 group,and the thickness of midgut muscle layer in T10 group was significantly higher than that in T40 group.A large number of cytoplasmic vacuolated hepatocytes appeared in the liver and pancreas of M.salmoides for in each group.There were no obvious inflammation in T20 and T40 group,but few inflammatory cells infiltrated around the blood vessels in the T0,T10,and T30 groups,and mass of inflammatory cells infiltrated around the blood vessels in NC30 group.The results show that the bacterium enzyme synergistic fermented soybean meal could reduce intestinal inflammation effectively.3.Effect of bacterium enzyme synergistic fermented soybean meal on intestinal flora of M.salmoides.Three fishes were picked randomly and the hindgut were taken for intestinal flora analysis after the feeding experiment.The OTU analysis and relative abundance analysis results showed there was no significant difference in Chao index and Ace index among groups T10,T40 and T0(P>0.05),revealed that there was no significant effect on the intestinal flora richness of M.salmoides for bacterium enzyme synergistic fermented soybean meal.The Chao index of NC30 group was significantly lower than that of the T0group(P < 0.05),indicating that ordinary soybean meal had a significant effect on the intestinal flora richness of M.salmoides.The Shannon index decreased gradually with the increase of the level of fish meal replaced by bacterium enzyme synergistic fermented soybean meal.The Shannon index of T40 group was significantly lower than the T0 group,indicating that the bacterium enzyme synergistic fermented soybean meal had a significant effect on the intestinal flora diversity of M.salmoides(P < 0.05),while the Shannon index of the T0 group is the highest,indicating that the intestinal flora diversity of the T0 group is the most complicated.The intestinal flora mainly consists of Proteobacteria,Tenericutes,Fusobacteria,and Firmicutes,which account for 95% of microflora in every group.The replacement of fish meal by bacterium enzyme synergistic fermented soybean meal had no significant effect on the relative abundance of Proteobacteria,Fusobacterium,and Pachyphyta(P > 0.05),but could increases the relative abundance of Pyrophyta significantly(P < 0.05).The most abundant genus are Mycoplasma,Cetobacterium,Plesiomonas and Aeromonas,among which the bacterium enzyme synergistic fermented soybean meal could increased the relative abundance of Mycoplasma significantly(P <0.05),while had no effect on the rest genus.All in all,the replacement of fish meal by bacterium enzyme synergistic fermented soybean meal could affect the growth performance,tissue biochemical indicators,digestive enzyme activity,midgut,liver and intestine tissue structure,and intestinal flora of M.salmoides significantly.It is suggested that the replacement ratio should not exceed 30%. |
