Effects of Replacement of Fish Meal by Fermented Soybean Meal on Growth Performance, Body Composition, Serum Biochemical Indices and Liver Tissue Morphology of Juvenile Large Yellow Croaker(Larimichthys crocea)

A 56 d feeding experiment was conducted to investigate the effects of replacement of fish meal by fermented soybean meal ( FSM) on growth performance, body composition, serum biochemical indices and liver tissue morphology of juvenile large yellow croaker ( Larimichthys crocea ) , and to find the suitable re?placement proportion of fish meal by FSM in diets of juvenile large yellow croaker. A 40% fish meal basal diet was formulated using fish meal and wheat gluten meal as main protein sources, and fish oil, soybean oil and soybean lecithin as main lipid sources. Six isonitrogenous ( protein level was 45%) and isolipidic ( lipid level was 10%) experimental diets were formulated by replacing 0 ( R0 group, as control group ) , 15% ( R15 group) , 30% ( R30 group) , 45% ( R45 group) , 60% ( R60 group) and 75% ( R75 group) fish meal with FSM on the basis of the basal diet, respectively. All diets were supplemented with crystalline amino acids such as lysine and methionine except the control group diet. The feeding experiment was carried out in three sea?ca?ges (1.5 m×1.5 m×2.0 m) of every group and each sea?cage had 60 juvenile large yellow croaker with initial body weight of (10.49±0.03) g. The results showed as follows: no significant difference in survival rate (SR) was found among groups (P>0.05), but with the increase of replacement proportion of fish meal by FSM, the SR showed a downward trend. The specific growth rate ( SGR) , weight gain rate ( WGR) and feed conversion ratio ( FCR) in R15, R30 and R45 groups had no significant differences compared with R0 group ( P>0.05); to increase the replacement proportion of fish meal by FSM ( R60 and R75 groups) , the SGR and WGR were significantly decreased ( P 0.05) , but whole body ash content has an upward trend with the increase of replacement proportion of fish meal by FSM. Serum biochemical indices in all groups were not significantly different ( P>0.05) , but serum total cholesterol content had a downward trend and serum alanine amino transferase activity had an up?ward trend with the increase of replacement proportion of fish meal by FSM. From the liver histological obser?vation, replacement proportion of fish meal by FSM more than 30% caused damage to the liver cells, and the replacement proportion was higher, the symptom was more serious. Comprehensive all measured indicators, we suggest that FSM replacement 30% fish meal in the diet containing 40% fish meal of juvenile large yellow croaker is suitable, but high replacement proportions cause the pathological changes of liver tissue and the de?crease of growth rate and SR.