Growth, immune response and resistance to Aeromonas hydrophila of juvenile yellow catfish, Pelteobagrus fulvidraco, fed diets with different arginine levels

An 84-day feeding trial was conducted to determine the dietary arginine requirement of juvenile yellow catfish, Pelteobagrus fulvidraco. Six isonitrogenous and isolipidic diets (45% protein and 7% lipid) were formulated to contain six graded dietary arginine levels ranging from 1.59 to 3.30% (dry weight) in about 0.4% increments. Each diet was randomly assigned to triplicate groups of 20 juvenile fish (2.00 ± 0.02 g) twice daily to apparent satiation. The results indicated that the highest weight gain and feed efficiency were observed in fish fed diet with 2.74% arginine. Red blood cell, hemoglobin and hematocrit significantly increased with increase of dietary arginine levels, whereas serum superoxide dismutase, glutathione peroxidase activities and malondialdehyde contents decreased. Fish fed the diet containing 2.74% arginine level showed the highest arginase, nitric oxide synthase, lysozyme activities, phagocytic index and respiratory burst among all treatments. Cumulative mortality of yellow catfish 14 days post-challenge with Aeromonas hydrophila was not significantly different. A quadratic regression analysis on specific growth rate against dietary arginine levels indicated that the optimal dietary arginine requirement was estimated to be 2.38% of the diet (corresponding to 5.29% of dietary protein). A dietary concentration of 2.38-2.74% arginine is recommended for juvenile yellow catfish to improve growth performance, immunity and disease resistance.