Dietary Methionine, Lysine And Arginine Requirements Of Juvenile Wuchang Bream (Megalobrama Amblycephala)

9-week or 10-week feeding trials were conducted to examine the effects of dietary methionine, lysine and arginine on feeding, growth performance, body composition, hematology, immune response and oxidation resistance in M. amblycephala in outdoor pond with cribs (1 m× 1m× 1 m). Six isonitrogenous and isoenergetic semi-purified experimental diets, using fish meal, casein and gelatin as intact protein sources supplemented with a crystalline amino acid mixture and soybean oil as the lipid source, were formulated to contain graded levels of methionine, lysine, and arginine, respectively, replaced by the same proportions of glycine. The experimental results are presented as follows:1. At the initiation of the experiment, the fish was fasted for 24 h and weighed. Fish of similar sizes (initial weight being 3.34 ± 0.03 g) were randomly chosen and sorted into eighteen cages with 30 fish per cage. Each experimental diet (The final levels of methionine were 0.39%、0.56%、0.85%、1.0%、1.24%.1.54%) was randomly assigned to triplicate tanks in a completely randomized design. The feeding trial lasted for 9 weeks. Results showed that final body weight (FBW), specific growth rate (SGR), protein efficiency ratio (PER), protein productive value (PPV), nitrogen retention efficiency (NRE) significantly increased with increasing dietary methionine levels from 3.9 g kg-1 to 12.4 g kg-1 and thereafter kept stable, while feed conversion ratio (FCR) showed an adverse trend. Compared to fish fed control diet (0.39% methionine diet), FBW, WGR, SGR and PPV were significantly improved when fish fed 0.85%、1.0% and 1.24% methionine diet (P<0.05), PER was significantly increased when fish fed 1.24% methionine diet (P<0.05), NRE was significantly added when fish fed 0.85% and 1.0% methionine diet (P<0.05). No significant differences were observed in condition factor (CF), hepatosomatic index (HSI) and viscerosomatic ratio (VR) of fish fed different dietary methionine levels (P>0.05). Protein content of the whole body showed an increasing trend with increasing dietary methionine level, while the reverse was observed in the whole body lipid content (P<0.05), but no significant differences were observed on moisture and ash among treatment groups (P>0.05). The complement were not significantly different among groups, except complement 3 (C3) in fish fed 0.56%、0.85% and 1.0% methionine diet and was significantly higher than those fish fed the control diet (P<0.05). Superoxide dismutase (SOD) of fish fed 0.85% and 1.0% methionine diet was significantly higher than those fish fed the control diet (P<0.05). The EAA contents of plasma in different groups were significantly (P<0.05) affected excluding leucine (Leu), isoleucine (Ile) and threonine (Thr) (P<0.05). The total EAA content was significantly increased with increasing dietary methionine levels (P<0.05) and thereafter kept a level (P>0.05). Aspartate alanine amino transferase (AST) activity in the fish fed 1.24 and 1.54% dietary methionine levels was significantly (P<0.05) higher than in those fish fed 0.39,0.56 and 0.85% methionine diet, while no significant differences were observed in alanine aminotransferase (ALT) (P>0.05). Plasma total protein (TP) content significantly (P<0.05) decreased with increasing dietary methionine level from 0.39% to 1.0%, and thereafter kept stable (P>0.05). Plasma urea content in the fish fed 0.39% dietary methionine level was significantly lower than in those fish fed 0.85% methionine diet (P<0.05). No significant differences were observed on glucose content among the treatment groups (P>0.05). Hemoglobin content (HGB), red blood cell count (RBC) and white blood cell count (WBC) significantly (P<0.05) increased with increasing dietary methionine level from 0.39% to 1.0%, however there was a significant (P<0.05) decreasing trend with increasing dietary methionine levels from 1.0% to 1.54%. Compared to those fish fed the control diet, cysteine sulfinic acid decarboxylase (CSAD) content of liver methionine diet significantly increased when fish fed 0.56% and 0.85% methionine diet (P<0.05), glutamic oxalo acetic transaminase (GOT) significantly improved when fish fed 0.85%,1.24% and 1.54% methionine diet (P<0.05), while no significant were not observed in glutamic pyruvic transaminase (GPT) and cysteine dioxgenase (CDO) (P>0.05). With increasing dietary methionine level, taurine content of muscle, liver, intestine, brain and eye significantly increased (P<0.05). Statistic data also showed that after infection with A. hydrophila, the cumulative mortalities of fish fed optimum methionine diet significantly decreased (P<0.05). The optimum methionine requirements were estimated to 0.85% and 0.84% of diet (2.5% and 2.47% of protein) based on SGR and PPV versus different dietary methionine levels, respectively, using broken-line regression analysis.2. At the initiation of the experiment, the fish was fasted for 24 h and weighed. Fish of similar sizes (initial weight being 3.34±0.03 g) were randomly chosen and sorted into eighteen cages with 30 fish per cage. Each experimental diet (The final levels of lysine were 1.29%,1.71%、2.09%、2.48%、2.88%、3.27%) was randomly assigned to triplicate tanks in a completely randomized design. At the end of feeding trial, final body weight (FBW), weight gain rate (WRG), specific growth rate (SGR), nitrogen retention efficiency (NRE), protein productive value (PPV) and protein efficiency ratio (PER) of fish fed diet containing 2.48% lysine were significantly higher than those fish fed control diet (1.29%) while feed conversion ratio (FCR) showed a adverse tendency, but no significant differences was observed in survival rate (SR) of fish fed different dietary lysine levels. Increased crude protein and reduced viscerosomatic ratio (VR) were observed in fish fed 2.48%lysine diet. Ash of whole body of fish fed 2.88% and 3.27% lysine diet was significantly higher than those fish fed 1.29% lysine diet (P<0.05). No significant differences were observed in condition factor (CF), hepatosomatic index (HSI), crude lipid and moisture of fish fed different dietary lysine levels (P>0.05). Alanine aminotransferase (ALT) activity and total protein (TP) contents were significantly improved with increasing lysine levels up to 3.27%(P<0.05). Urea content in plasma of fish fed 2.94% lysine diet was significantly lower than those fish fed 1.29% lysine diet (P<0.05). while Aspartate alanine aminotransferase (AST) activity and glucose (Glu) were not significantly altered (P>0.05). The EAA contents of plasma in different groups were significantly affected excluding leucine (Leu) and valine (Val) (P<0.05). The total EAA content was significantly increased with increasing dietary lysine levels (P<0.05) and thereafter kept a level (P>0.05). Hemoglobin content (HGB), red blood cell count (RBC) and white blood cell count (WBC) significantly (P<0.05) increased with increasing dietary lysine level from 1.29% to 2.09%, however there was a significant (P<0.05) decreasing trend with increasing dietary lysine levels from 2.09% to 3.27%. The complement were not significantly different among groups (P>0.05), except complement 3 (C3) in fish fed 2.48% lysine diet and was significantly higher than those fish fed the control diet (P<0.05). Superoxide dismutase (SOD) of fish fed 2.48% lysine diet was significantly higher than those fed the control diet (P>0.05). Statistic data also showed that after infection with A. hydrophila, the cumulative mortalities of fish fed optimum lysine diet significantly decreased (P<0.05). On the basis of SGR and PPV, the optimum dietary lysine requirement of juvenile M. amblycephala was estimated to be 2.36% of diet (6.94% of protein) and 2.22% of diet (6.53% of protein), respectively, using broken-line regression analysis.3. At the initiation of the experiment, the fish was fasted for 24 h and weighed. Fish of similar sizes (initial weight being 2.60 ± 0.01 g) were randomly chosen and sorted into eighteen cages with 30 fish per cage. Each experimental diet (The final levels of arginine were 0.83%、1.30%,1.81%、2.35%、2.82%、3.36%) was randomly assigned to triplicate tanks in a completely randomized design. At the end of the feeding trail, the results showed survival rate (SR) was not significantly affected by dietary arginine level (P>0.05). Finial weight, specific growth rate (SGR), feed efficiency ratio (FER), protein efficiency ratio (PER) and protein productive value (PPV) increased with increasing dietary arginine level from 0.83 to 1.81%(P<0.05), thereafter showed declined trend but the differences were not significant (P>0.05). There were no significant differences in whole body composition among the treatments (P>0.05). The arginine content was significantly increased with increasing dietary lysine levels (P<0.05), while lysine content of plasma showed a adverse trend. Compared to control diet (0.83%), urea, total protein (TP) and globulin (GLB) concentration significantly improved (P<0.05), but reduced aspartate aminotransferase (AST) activity of plasma, while there was a significantly difference in glucose (Glu) concentration, alanine aminotransferase (ALT) activity and albumin (ALB) of plasma in juvenile blunt snout bream (P<0.05). Total nitric oxide synthase (TNOS) and inductivity nitric oxide synthase (iNOS) activity on plasma of fish fed 2.82% arginine diet were significantly higher than those fish fed control diet (P<0.05), while no significant differences were observed in constitutive nitric oxide synthase (cNOS) (P>0.05). Constitutive nitric oxide synthase (cNOS) activity on head-kidney of fish fed 2.35% arginine diet were significantly higher than those fish fed control diet (P<0.05), while no significant differences were observed in total nitric oxide synthase (TNOS) and inductivity nitric oxide synthase (iNOS) activity (P>0.05). Hemoglobin content (HGB) content, red blood cell (RBC) count and white blood cell (WBC) count significantly (P<0.05) increased with increasing dietary arginine level from 0.83% to 1.81%, however there was a significant (P<0.05) decreasing trend with increasing dietary arginine levels from 2.35% to 3.36%. Maximum of RBC count, WBC count and HGB content were observed in 1.81%. The complement were not significantly different among groups, except complement 3 (C3) in fish fed 1.81% and 2.35% arginine diet and was significantly higher than those fish fed the control diet (P<0.05). There were no significant differences in plasma SOD activities among dietary treatments (P>0.05). Dietary arginine level significant affected the respiratory burst assay of blood cell (P<0.05), while an adverse trend was observed in cumulative mortality in juvenile M. amblycephala infected with A. hydrophila. Based on SGR and FER, the optimal dietary arginine requirements of juvenile M. amblycephala were estimated to be 1.70% of the diet (5.00% of dietary protein) using broken-line regression analysis.