Abstract:
To investigate the effects of chronic external ammonia stress on growth, immunity and metabolism of juvenile GIFT tilapia (
Oreochromis niloticus), we designed five concentrations of ammonia, including 0 mg · L
-1(A
0), 1.63 mg · L
-1(A
1), 3.25 mg · L
-1(A
2), 6.51 mg · L
-1(A
3) and 13.01 mg · L
-1(A
4). The results show that after 30-day feeding, the juveniles′ weight gain rate (WGR) and specific growth rate (SGR) decreased significantly with increasing concentration of ammonia. For immunity, the number of white blood cells (WBC) increased but that of hemoglobin (HGB) decreased with increasing concentration of ammonia. Serum albumin(ALB) concentration and superoxide dismutase(SOD) activities of A
3 and A
4 were significantly less than A
0, while alkaline phosphatase (AKP) concentration of A
4 was significantly less than A
0. For metabolization, serum triglycerides(TG) concentration of A
3 and A
4 were significantly less than A
0, while total cholesterol (TC) concentration of A
1~A
4 were significantly less than A
0. Serum alanine transaminase(ALT) activities of A
3 and A
4 were significantly less than A
1 and A
2. Meanwhile, only aspartate transaminase (AST) activities of A
4 was less than A
0. It is revealed that the growth, nonspecific immunity and metabolism of juvenile GIFT tilapia would be inhibited under chronic ammonia stress; change of ammonia concentration in tilapia aquaculture should be paid more attention to.
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