| In this paper,two experiments were designed to investigate the effects of replacing fish meal（FM）with soybean meal（SBM）protein and the substitution of FM protein by SBM protein in 5 ppt salinity on the growth performance,feed utilization,body composition and physiological state of juvenile Liza haematocheila.The main results are as follows:Experiment 1:Effects of replacing fish meal with soybean meal protein on growth performance,feed utilization and serum biochemical indices of juvenile Liza haematocheila.Five test diets were formulated to replace fish meal（FM）protein by soybean meal（SBM）protein at 0%,25%,50%,75%,or 100%（named as SBM0,SBM25,SBM50,SBM75,SBM100,respectively）.Three replicate samples were set for each diet,and each replicate sample was fed with 20 fish(starting average weight 5.08±0.11 g fish-1).The results as showed:no significant effects were observed in weight gain（WG）,feed efficiency（FE）,and protein efficiency ratio（PER）between SBM0 and SBM75 diets（P>0.05）.But,the WG,FE,and PER values showed a downward decreased trend when fish fed SBM75 diet（P<0.05）.Fish fed diet with SBM100 has the highest daily feed intake（DFI）value.The value of hepatosomatic index（HSI）decreased significantly with dietary SBM levels increased（P<0.05）.Negative linear were observed between SBM content and energy retention（ER）and lipid retention（LR）.Levels of serum triacylglycerol（TG）and total cholesterol（T-CHO）decreased significantly as the dietary SBM levels increased（P<0.05）.FM substitution with different levels of SBM had no statistic differences in the activities of trypsin,lipase（LPS）,and amylase（AMS）in the intestine（P>0.05）.Activities of superoxide dismutase（SOD）,catalase（CAT）,and glutamyl oxaloacetic transaminase（GOT）in the liver increased significantly with dietary SBM levels enhanced（P<0.05）.While the concentration of malondialdehyde（MDA）decreased significantly with dietary SBM levels elevated（P<0.05）.The broken-line model of WG and FE showed the acceptable level of SBM to replace FM was 51.18%～52.46%for L.haematocheila.Experiment 2:Effects of replacing fish meal with soybean meal on growth performance,feed utilization and serum biochemical indices of juvenile Liza haematocheila in low salinityIn this experiment,six test diets were prepared to 0%,25%,50%,75%,75%+taurine and 100%（L-SBM0,L-SBM25,L-SBM50,L-SBM75,L-SBM75+T and L-SBM100）soybean meal（SBM）protein level to replace fish meal（FM）protein.Three replicate samples were set for each diet,and each replicate sample was fed with 20 fish(average weight 6.74±0.10 g fish-1).The results as showed:the survival of L.haematocheila in low salinity ranged from 90.48%to 100%,and there was no statistical difference among all treatments（P>0.05）.L.haematocheila fed L-SBM0,L-SBM25 and L-SBM50 diets had no significant differences in FBW,WG,SGR and FE（P>0.05）,but L-SBM0 diet had significantly higher SGR values than L-SBM75,L-SBM100 and L-SBM75+T diets（P<0.05）.There were no significant differences between viscerosomatic index（VSI）and condition factor（CF）among the treatment groups（P>0.05）,while the values of IPF and HSI decreased significantly with SBM level increased（P<0.05）.The DNG and NR values in L-SBM0、L-SBM25 and SBM50diets was significantly higher than that of the L-SBM75,and L-SBM75+T diets（P<0.05）.With SBM replace levels increased,DEG,DLG and LR decreased significantly（P<0.05）.The crude lipid content decreased significantly with SBM content increased（P<0.05）.Serum GLU increased significantly with SBM content increased（P<0.05）.Serum TG and T-CHO levels decreased significantly with SBM content increased（P<0.05）.Intestinal trypsin activity in L-SBM0 diets was significantly higher than that in L-SBM100 diet（P<0.05）.The level of CAT in liver decreased significantly with SBM levels increased（P<0.05）.The concentration of MDA in liver increased significantly with the increase of SBM levels（P<0.05）.GPT activity in L-SBM0 diet was significantly lower than the other treatment groups（P<0.05）.The broken-line model of WG and FE showed the acceptable level of SBM to replace FM was 48.68%～48.73%for L.haematocheila in low salinity. |
