Dietary copper requirement of juvenile Oriental river prawn Macrobrachium nipponense, and its effects on growth, antioxidant activities, and resistance to Aeromonas hydrophila

The present experiment evaluated the effects of dietary copper (Cu) on growth, antioxidant activities, and susceptibility to Aeromonas hydrophila infection of juvenile Oriental river prawn Macrobrachium nipponense, as well as determining the optimal dietary copper requirement. Semi-purified diets containing seven graded levels of copper (2.8, 12.2, 20.9, 29.8, 43.1, 78.9 and 157.1 mg/kg diet) from CuSO₄·5H₂O were fed to juvenile prawn (initial weight 0.101±0.002 g). The weight gain of prawns fed with 2.8-78.9 mg/kg Cu was higher and they had lower feed conversion ratios than the group fed 157.1 mg/kg Cu. Cu concentrations in the hepatopancreas, muscle, and whole body in prawns tended to increase with increased dietary Cu concentration. Hepatopancreas Cu-Zn superoxide dismutase (Cu-Zn SOD) activity, glutathione peroxidase (GPx), and total antioxidant competence (T-AOC) were highest (P<0.05) in the 43.1 mg/kg Cu group. The hepatopancreas malondialdehyde (MDA) content was lower (P<0.05) in the prawns fed 29.8 mg/kg Cu than that in prawns fed 2.8, 12.2, 78.9 and 157.1 mg/kg Cu. After the feeding experiment, prawns were injected with A. hydrophila, and the cumulative mortality rate of the prawns fed with 20.9-43.1 mg/kg Cu was lower than the prawns fed with 2.8 and 157.1 mg/kg Cu. The optimum requirement of dietary Cu in juvenile prawns was estimated at 26.9-27.8 mg/kg diet based on cumulative mortality rate and whole-body Cu retention.