Effects Of Substituting Fishmeal With Soybean Meal On Growth Performance And Intestinal Healthy In Japanese Seabass (Lateolabrax Japonicus)

An 8-week feeding trial was conducted to investigate the effects of substituting fishmeal with soybean meal on growth performance,intestinal healthy in Japanese seabass(initial body weight(6.67�0.03 g).Three isonitrogenous(crude protein 43%)and iso-lipidic(13%)practical diets were formulated by replacing 0%(D1),50%(D2)and 75%(D3)of protein from FM(Fish meal)with SBM(Soybean meal).Each diet was randomly fed to triplicate treatments of fish,and20 individuals were stocked in each tank,and fed twice daily to apparent satiation.The results are shown as follows:1.Effects on growth performance,body composition,digestive enzyme activities and apparent digestibility coefficients by replacing fish meal by soybean meal of Japanese seabass.The lowest and highest values of weight gain(WG),specific growth rate(SGR),feeding efficiency(FE),protein efficiency ratio(PER)and survival rate(SR)appeared in the groups of D3 and D1,respectively.The moisture and crude ash in whole-body were significantly increased;whereas,the crude lipid and crude protein were significantly decreased in D3(P>0.05).The digestive enzymes activities,apparent digestibility coefficients(ADC)of protein,gross energy and dry matter decreased,in contrast to increasing of the SBM.The above results indicated that increasing the amount of soybean meal in the diets of Japanese seabass leads to decrease growth performance and affect whole-body composition by reducing digestive enzymes activities and increasing intestinal harm.2.Effects of substituting fishmeal with soybean meal on intestinal histology and morphometry in Japanese seabass.With increasing of the SBM,the villus height,villus width,musule thickness and villus length to crypt depth ratio significantly decreased.Gross qualitative observations of proximal intestine and mid-intestine sections revealed that fish fed the D2 or D3 diet samples had unhealthy and inflamed intestines(epithelial cell remained sparse,epithelial cells arranged disorder,lamina propria widening)compared to fed D1 diet.Soybean meal substituting fishmeal significantly increased the concentration of D-lactate in serum(P<0.05).There were nosignificant difference between DAO activity of D1 and D2 in serum,however the DAO activity was significantly increased in D3.The results indicate that Soybean meal replaces the fish meal through destructing the intestinal morphology structure of Japanese seabass,and then induces a negative influence on the digestion and absorption of nutrients and immune function.3.Effects of substituting fishmeal with soybean meal on intestinal peptide,amino acid transporters and inflammatory factor mRNA expression in Japanese seabass.Compared with the D3 group,the D2 and D1 groups increased the expression of SLC1A5,LAT1 and PepT1.Adding soybean meal,the TNF-?,IL-1? and IL-2 expression were significantly increased in proximal intestine and mid-intestine(P<0.05),while there was no significant difference in expression of IL-8 in mid-intestine(P>0.05).Soybean meal substituting fishmeal could significantly decreased IL-4mRNA expression in mid-intestine of Japanese seabass(P<0.05).The expression of IL-10 mRNA was significantly increased in D2 group in proximal intestine(P<0.05).The expression of IL-10 mRNA was significantly increased in D3 group in mid-intestine(P<0.05).The results indicates that feed ingredients could affect the intestinal absorption ability of nutrients by affecting the expression of nutrient transporter gene,and the anti nutritional factors in soybean meal can destroy the balance of anti-inflammatory and proinflammatory cytokine gene expression,and then cause intestinal damage.4.Effects of substituting fishmeal with soybean meal on intestinal microflora in Japanese seabass.Microbial genome sequencing showed that: Soybean meal substituting fishmeal did not change the variety of intestinal flora but affected the number of intestinal flora.Soybean meal substituting fishmeal did not change the variety of intestinal dominant bacterial community,however affected the number of intestinal dominant bacterial community.The number of harmful bacteria(Pseudomonas,Acinetobater,Enterobacter,Lactococcus)increased as SBM increased,while the beneficial bacteria(Bacillus)decreased.