Effects of lysine-arginine interaction on growth performance, body composition,and muscle amino acid levels of juvenile turbot(Scophthalmus maximus L.)

A feeding experiment was conducted to investigate the effects of lysine,arginine and their interaction on the growth performance,whole body composition and muscle amino acid levels of juvenile turbot(Scophthalmus maximus L.)initial weight(18.48±0.16)g.Nine isonitrogenous and isoenergetic diets according to a 3×3 factorial were designed:the basal diet as the control diet supplemented with three levels of arginine(0%,0.9% and 2.0%)crossed with lysine(0%,1.19% and 2.39%).Each diet was randomly allocated to triplicate groups of juvenile turbots for 10 weeks.The results showed that the weight gain rate(WGR)and specific growth rate(SGR)were significantly increased at the level of lysine(1.19%)supplement diets(P<0.05),while the addition of arginine had no additional effect(P>0.05).Dietary lysine and arginine had significant interactions on feed efficiency rate(FER),protein efficiency rate(PER),protein retention(PR)and crude protein content(P<0.05),the maximal value of which was obtained at the levels of lysine(1.19%)and arginine(0.9%)supplement diet.However,weight gain(WGR),the specific growth rate(SGR),crude lipid content,ash and body indexes were not affected by the interaction of arginine and lysine(P>0.05).Crude lipid content and moisture were decreased with the increased levels of lysine(P<0.05),while the gradient arginine showed no significant effect(P>0.05).Hepatosomatic indexes(HSI)and visceral indexes(VSI)were greatly reduced with the increased levels of both lysine and arginine(P<0.05).Dietary lysine and arginine had significant interactions on majority muscle individual amino acid levels,the minimum value of which was obtained at the levels of lysine(2.39%)and arginine(0.9%)supplement diet(P<0.05).It was concluded that lysine and arginine had interaction for the aspects of feed efficiency,body protein retention and muscle individual amino acid levels,while the interaction effect of the growth and body index does not exist;juvenile turbot maintained maximal growth and feed efficiency at the supplement levels of lysine(1.19%)and arginine(0.9%);compared to arginine,lysine seems to be the major factor,proper supplementation promotes growth,while excessive level inhibits turbot growth,feed efficiency and muscle amino acids retention through the antagonism with arginine.