Effects of dietary arginine and lysine on growth and non-specific immune responses of juvenile darkbarbel catfish(Pelteobagrus vachelli)

An 8-week feeding trial was conducted to estimate the effects of dietary arginine(Arg)and lysine(Lys)on growth and non-specific immune responses of juvenile darkbarbel catfish.Nine diets(42% crude protein and 10% crude lipid)were formulated to contain three Arg levels(2.41%,4.86% and 6.81% of dietary protein),and each with three Lys levels(1.95%,5.84% and 8.27% of dietary protein).Each diet was randomly fed to triplicate groups of darkbarbel catfish［initial body weight:(2.12±0.01) g］to apparent satiation and each group was stocked with 30 fish.At the termination of the feeding trial,growth and non-specific immune parameters were monitored.The results showed dietary arginine and lysine had significant effects on the specific growth rate(SGR)and the respiratory burst activity of head kidney macrophages of juvenile darkbarbel catfish(P<0.05).The appropriate content of diet arginine/lysine was 6.81/5.84 dietary protein based on the growth,but the respiratory burst activity of headkidney macrophages was the highest when arginine/lysine was 4.86/8.27 dietary protein.Dietary Arg had significant effects on the serum nitricoxide synthase(NOS)activity of juvenile darkbarbel catfish(P<0.05).The activity of NOS was higher in fish fed appropriate or high Arg levels than low Ary levels.No significant differences were found in the serum arginase(ARG)and catalase(CAT)(P>0.05)among dietary treatments.In the present study,significant interactions of dietary arginine and lysine were found on growth of juvenile darkbarbel catfish,but not on the body composition,hepatosomatic index(HSI),and serum NOS,ARG and CAT activity.