The supplementation of dietary selenium yeast and green tea-derived polyphenols improves antioxidant capacity and immune response in juvenile Wuchang bream under ammonia stress

摘要

In order to investigate protective effects of dietary selenium yeast and green tea-derived polyphenols on ammonia stress, healthy Wuchang bream juveniles (3.24 +/- 0.08 g) were fed basal diets and three treatment diets supplemented with 0.50 mg/kg selenium yeast, 50 mg/kg green tea-derived polyphenols, and combination of 0.50 mg/kg selenium yeast and 50 mg/kg green tea-derived polyphenols, respectively. After a 60-day feeding, fish were exposed to 22.5 mg/L total ammonia nitrogen for 48 hr. The results showed that total antioxidant capacity, catalase and glutathione peroxidase in the serum were higher in three treatment groups than in control group before and after ammonia exposure (p .05), while serum cortisol was lower in three treatment groups (p .05). Similarly, the content and mRNA levels of splenic interleukin 1 beta, tumour necrosis factor alpha and immunoglobulin M showed significant increases in three treatment groups in relative to the controls (p .05). Splenic lesions for three treatment groups were less severe, and the healing process of the lesions was faster than the control group after ammonia exposure. These findings demonstrated that single and combined supplementation of selenium yeast and green tea-derived polyphenols could enhance antioxidant and immune responses to alleviate oxidative stress and damage by ammonia. Overall, the combination of selenium yeast and green tea-derived polyphenols has a potential use as a preventive or therapeutic measure in ammonia-exposed fish.