The protective effects of dietary garlic on common carp (Cyprinus carpio) exposed to ambient ammonia toxicity

The present research aimed to investigate the potential effects of dietary garlic supplementation on the health status of common carp (Cyprinus carpio) exposed to ambient ammonia toxicity. The fish were fed with either of 0 (control), 0.5, 1 and 1.5% garlic levels for 35 days. They were then challenged with 0.5 mg/L ambient unionized ammonia-nitrogen for 3 h. Blood samples were taken before and after ammonia exposure to measure the antioxidant, enzymatic and immune responses of common carp. The results showed that garlic administration significantly decreased plasma glucose, cortisol and malondialdehyde (MDA) levels, and alanine transaminase (ALT), alkaline phosphatase (ALP), aspartate transaminase (AST) and glutathione peroxidase (GPX) activities. Also, it significantly increased plasma catalase (CAT), lysozyme, alternative complement (ACH50) and bactericidal activities, and immunoglobulin level, but had no effect on plasma superoxide dismutase activity. Ammonia exposure led to significant increases in plasma cortisol, glucose, MDA, SOD, CAT, GPX, ALT, AST, and ALP and decreases in ACH50, total Ig, bactericidal activity. Garlic supplementation significantly mitigated stress, oxidative stress and changes in plasma enzymatic activities in the fish exposed to ammonia. In conclusion, the current results suggest that dietary administration of garlic, especially at 1 and 1.5%, has beneficial effects to improve plasma antioxidant and immunological parameters and it was effective to mitigate the adverse effects of ammonia toxicity on antioxidant, enzymatic and immune responses in common carp.