The Requirement Of Lysine And Methionine For Grouper (Epinephelus Coioides) At Two Growth Stage

Feeding trials were conducted to investigate the effects of dietary lysine and methionine levels on the growth performence,body composition and hemolymph biochemical,enzyme activities in liver of grouper(Epinephelus coioides)at two different growth stages.The brief summarys are as follows1.Seven isonitrogenousand isolipidic diets that Diet 1 with fish meal as the sole protein source was used as a reference.Amino acids test Diets 2~7 with graded levels of lysine 2.03%?2.38%?2.81%?3.26%?3.63%?4.08% in juvenile grouper(initial weight of 22.07±0.12g)and 1.61%?2.04%?2.44%?2.76%?2.98%?3.35% in subadult grouper(initial weight of 102.51±0.15g).Each diet was fed to three replicate groups of grouper were hand fed twice daily to apparent satiation.The results showed that fish fed the reference diet had significantly higher WG,SGR,PER,protein contents of whole body,also the GPT and survival in juvenile grouper and the CF in subadult grouper(P<0.05).Among other trealanents fed the diets containing CAAs,increasing dietary lysine WGR and SGR increased and then decreased in two different growth stages.FCR decreased and then increased in juvenile grouper,but subadult grouper had not significantly different among treatment(P>0.05).Survival was not significantly different among treatment(P>0.05).In two growth stage,GLU,CHOL,TG,SOD and CAT was significantly affected by dietary lysine levels(P<0.05).Based on SGR,it is recommended that the diet for two stages groupers shoud contain lysine at 3.04% and 2.61% of dry diet,corresponding to 6.33% and 5.80% of dietary protein on a dry weight basis by quadratic regression analysis.2.Seven isonitrogenousand isolipidic diets that Diet 1 with fish meal as the sole protein source was used as a reference.Amino acids test Diets 2~7 with graded levels of methionine 0.71%?0.98%?1.26%?1.57%?1.86%?2.18% in juvenile grouper(initial weight of 9.75±0.05g)and 0.69%?0.85%?0.99%?1.19%?1.43%?1.58% in subadult grouper(initial weight of 102.60±0.14g).Each diet was fed to three replicate groups of grouper were hand fed twice daily to apparent satiation.The results showed that fish fed the reference diet had significantly higher WG,SGR,PER,also the protein contents of whole body and GOT,GPT in juvenile grouper(P<0.05).FCR,VSI,SOD,and the juvenile grouper lipid contents of whole body,also the TG in subadult grouper had significantly lower than test group.Among other trealanents fed the diets containing CAAs,increasing dietary methionine WGR and SGR increased and then decreased in two different growth stages.FCR had not significantly different among treatment in juvenile grouper,but the 1.58% group of methionine levels had significantly higher among treatment in subadult grouper(P<0.05).Survival was not significantly different among treatment(P>0.05).In two growth stage,GLU,CHOL,TG,SOD and CAT was significantly affected by dietary lysine levels(P<0.05).the diet in the presence of 0.46% cystine(corresponding to 1.02% of dietary protein on a dry weight basis),based on SGR,it is it is recommended that for grouper should contain methionine at 1.58% and 1.27% of dry diet,corresponding to 3.51% and 2.82% of dietary protein on a dry weight basis by quadratic regression analysis.