EFFECTS OF VITAMIN E SUPPLEMENTATION ON GROWTH, IMMUNITY OF JUVENILE BLACK CARP (MYLOPHARYNGODON PICEUS) SUBJECTED TO AMMONIA-NITRITE STRESS

An 8-week feeding experiment was conducted to evaluate the effects of dietary vitamin E (VE) supplementation on growth, immunity of juvenile black carpinitial average weight of (7.270.40) g subjected to ammonia-nitrite stress. Six practical diets were formulated to contain 14.36 (control), 25.14, 37.66, 62.97, 113.92, and 210.45 mg vitamin E equivalent/kg diet, supplied as VE acetate. After feeding for 8 weeks, according to growth, the black carp in control, 62.97 and 210.45 mg/kg vitamin E treatment groups were selected and subjected to ammonia-nitrite stress (20 mg/L) for 24h. The results indicated that the dietary VE content for the maximum specific growth rate (SGR) was about 45.0 mg/kg. The vitamin E levels in the tissues of liver, muscle and the serum were positively correlation with diet vitamin E content, and no significant differences were observed among fish fed with the diets that had equal to or higher than 113.92 mg/kg of vitamin E. No significant difference in gill Na+/K+-ATPase (NKA) activity were observed among these treatments. However, with increasing diet vitamin E content, activities of total superoxide dismutase (T-SOD) and catalase (CAT) increased, and malondialdehyde (MDA) content decreased. Each group of muscle vitamin E concentration and CAT activity were not affected by ammonia-nitrite stress, although liver vitamin E concentration decreased significantly and serum VE level increased in the 62.97and 210.45 mg/kg VE treatments. After the stress, T-SOD and gill NKA activities in the control group decreased significantly and cortisol content increased significantly (P0.05). In comparison, activities of T-SOD, NKA and cortisol showed no significant changes. MDA content in each group increased significantly after stress. However, for the 210.45 mg/kg VE treatment group, MDA content was significantly lower than the control group (P0.05). Our results indicated that the effective VE requirement of juvenile black carp for optimal growth may be 45.0 mg/kg diet, and higher vitamin E in diet could improve non-immune response and anti ammonia-nitrite stress ability of black carp.