EFFECTS OF DIETARY SUPPLEMENTATION WITH GLUTATHIONE ON TISSUE GSH LEVEL, IMMUNITY, AND ANTIOXIDANT CAPACITY OF JUVENILE YELLOW CATFISH (PELTEOBAGURS FULVIDRACO)

To assess the effects of dietary supplementation with glutathione (GSH) on tissue GSH levels, immunity, and antioxidant capacity of juvenile yellow catfish (Pelteobagrus fulvidraco), a total of 800 yellow catfish with a mean body weight of (1.32±0.01) g were considered and randomly divided into 5 groups with 4 replicates per each group and 40 fish per each replicate as well. During 56d, the fish were fed by a basal diet and four test diets, which supplemented with 100, 300, 500, and 700 mg/kg of reduced GSH, respectively. The results indicated that, except for 100 mg/kg group, supplementation with GSH significantly increased the GSH content in liver and serum of yellow catfish (P<0.05). When GSH level was 300 mg/kg or higher, GSH content in liver and serum was in a stable state. With the increase of glutathione level, the immunity and antioxidant indices were initially increased, and then decreased. The lysozyme and alkaline phosphatase activities in 300 and 500 mg/kg groups, immunoglobulin M (IgM) and complement component 4 (C4) contents in 300 mg/kg group, and acid phosphatase activity in 500 mg/kg group markedly increased, compared with the control group (P<0.05). There were no significant differences (P>0.05) in complement component 3 (C3) and nitric oxide contents among all groups. Compared with the control and 700 mg/kg groups, the liver superoxide dismutase, catalase and glutathione peroxidase activities, total antioxidant capacity and the serum superoxide dismutase, as well as glutathione peroxidase activities in 300 mg/kg group were significantly higher (P<0.05), while the serum malondialdehyde content in that group was considerably lower (P<0.05). Under ammonia-nitrogen stress for 96h, compared with the control group, the liver and serum superoxide dismutase, catalase, and glutathione peroxidase activities in 300 mg/kg group were significantly greater (P<0.05), however, the serum malondialdehyde content in the mentioned group was significantly lower (P<0.05). In conclusion, dietary supplementation with GSH could enhance the tissue GSH level, immunity and antioxidant capacity of juvenile yellow catfish, and the effective range of this enhancement was 300 to 500 mg/kg as well.