Effects of chronic ammonia stress on growth, antioxidative and immunity indices in liver of juvenile Acipenser schrenckii

To preliminarily reveal the physiological response of juvenile Acipenser schrenckii to chronic ammonia-nitrogen stress, we exposed the juveniles to different ammonia nitrogen concentrations (0.01, 0.5, 1.0, 2.0 and 4.0 mg·L⁻¹) for 60 d, and investigated their growth, antioxidative and immunity indices. The results show that the weight gain rate (WGR), specific growth rate (SGR), viserosomatic index (VSI) and hepatosomatic index (HSI) of the juveniles decreased significantly with the increase of ammonia concentration (P<0.05). However, there was no significant change in condition factor (CF). Among the antioxidative indexes, the superoxide dismutase (SOD) , catalase (CAT) , total antioxidant capacity (T-AOC) activity and glutathione (GSH) content in liver decreased  gradually with the increase of ammonia concentration, while malondialdehyde (MDA) content increased gradually. Among the immune indices, lysozyme (LZM) activity and immunoglobulin M (IgM) content in the liver decreased significantly (P<0.05). The results suggest that the chronic ammonia stress inhibits the growth, antioxidative and immunity capacity of the juveniles significantly. Thus, in the actual breeding process of A. schrenckii, the ammonia concentration in water should be controlled at ≤0.5 mg·L⁻¹ to avoid the adverse effects of ammonia stress.