Effects Of Low-protein Diet And Maggot Meal Replacment Of Fishmeal On Growth Performance,Body Composition And Antioxidant Capacity Of Hybrid Yellow Catfish

With the rapid development of the aquaculture industry,the demand for diet materials is increasing,and the shortage of protein resources is a serious problem and challenge in the world.Low protein diet could conserve resources,effectively reduce the emission of nitrogen pollution of water environment,but would cause the decrease of nitrogen retention and reducing palatability,thereby causing negative effects of growth performance.Therefore,improve the utilization efficiency of protein in the body,and reduce nitrogen emissions without affecting the growth performance of fish has become an important problem in China.In this experiment,hybrid yellow catfish was used to evaluate the effects of supplementing methionine and lysine in low-protein diet and maggot meal replacement of fish meal on the growth performance,body composition and antioxidant capacity of hybrid yellow catfish The experiment would provide the theoretical basis and reference for the nutrition and diet of hybrid yellow catfish1.Effect of diets containing maggot meal(MGM)in substitution of fishmeal(FM)on growth performance and antioxidant capacity of hybrid yellow catfishSix isonitrogenous(crude protein content was 42%)experimental diets were formulated by replacing 0%(GO as control diet),20%(G20),40%(G40),60%(G60),80%(G80),and 100%(G100)of FM with MGM.Each diet was fed to triplicate groups of fish for 8 weeks,and the initial weight of fish is(0.62±0.01).Growth performance and antioxidant enzyme activity(SOD,CAT,GR,T-AOC)in liver tissue and serum were determined at the end of the trial.The results show:(1)Compared with the control diet,there was no significant effect on growth performance in G20 and G40(P>0.05),G60,G80 and G100 group showed a significant negative effect(P<0.05).Compared with the G0 diet,there was no significant effect on feed conversion ratio(FCR)in G20 and G40(P>0.05),G60,G80 and G100 group showed a significant negative effect(P<0.05).There was no significant effect on survival ratio between each diet.(2)There was no significant difference in body composition and physical indexes between hybrid yellow catfish in each group(P>0.05).(3)The activities of superoxide dismutase(SOD),catalase(CAT),and glutathione reductase(GR)in the serum and liver of hybrid yellow carp in the G20 group were slightly higher than those in the G0 group,but there was no significant difference(P>0.05),liver CAT activity and total antioxidant capacity(T-AOC)increased significantly in G40(P<0.05).GR and SOD activities in liver,SOD activity and T-AOC in serum decreased significantly in the G80 group(P<0.05).In summary,the fly pupae protein can replace 40%of fish meal without significantly negatively affecting the growth performance,body composition and antioxidant capacity of hybrid yellow catfish2.Effect of low protein diet supplementation with lysine and methionine on growth performance,body composition,serum biochemical indexes and antioxidant capacity of hybrid yellow catfishFive experimental diets were formulated and have 3 protein levels as 42%(control),37%(LP1)and 32%(LP2).Use the control diet as standard,formulate other 2 low-protein diets(37%and 32%)and supplementation with lysine and methionine(LP1+AA and LP2+AA).Each diet was fed to triplicate groups of fish for 8 weeks,and the initial weight of fish is(0.96±0.01)g.Growth performance and antioxidant enzyme activity(SOD,CAT,MDA,T-AOC)in liver tissue and serum were determined at the end of the trial.The results show:(1)Compared with the control group,there was no significant difference in the weight gain rate(WGR)and specific growth rate(SGR)of hybrid yellow catfish in the LP1+AA and LP2+AA diet(P>0.05)the WGR and SGR decreased significantly(P<0.05)in LP1 and LP2 diet.The Hepatosomatic index(HSI)in LP2 and LP2+AA diets was significantly higher than that in LP1 group and LP1+AA diet.(2)There was no significant difference in body composition and physical indexes between hybrid yellow catfish in each diet(P>0.05)(3)The triglyceride and total protein content of the LP2 group in serum was significantly lower than that in other diets(P<0.05),the glucose content of the LP1 and LP2 diets in serum was significantly lower than that of the control,LP1+AA and LP2+AA groups(P<0.05),There was no significant difference in cholesterol and urea nitrogen content between each diet in serum(P>0.05).(4)There was no significant difference in aspartate transaminase(AST)in serum and liver tissue between each diet(P>0.05),and there was no significant difference in alanine aminotransferase(ALT)in liver tissue between each diet(P>0.05)but LP1 and LP2 ALT activity in serum is significantly lower than that in control,LP1+AA and LP2+AA diet(P<0.05).(5)The activity of CAT in LP2 was significantly lower than that in other diets;T-AOC in serum in LP1,LP2 and LP2+AA diets was significantly lower than that in control and LP1+AA diet(P<0.05),and there was no significant difference in T-AOC in liver tissue between each diet(P>0.05).MDA content in serum in LP2 was significantly higher than that in control and LP1+AA diets,MDA content in liver tissue in LP2 was significantly higher than that in LP1+AA diet(P<0.05).In summary,reducing 5%protein of diet do not have significant effects of growth performance and antioxidant capacity in hybrid yellow catfish,reducing 5%and 10%protein of diet and without supplement of Lys and Met could cause negative effects of hybrid yellow catfish.