Effects of dietary protein and cellulose levels on growth performance, antioxidant status, immune response and inflammation in juvenile yellow catfish ( Pelteobagrus fulvidraco )

Abstract

In this study, nine experimental diets were formulated to contain three graded levels of protein (40, 45 and 50% of dry diet) and three graded levels of cellulose (0, 5 and 10% of dry diet). These diets were then fed in triplicate to yellow catfish for 90 days. We found that fish fed diets containing 45% and 50% protein had more weight gain than did fish fed a 40% protein diet, while fish fed diets supplemented with 5% cellulose achieved the greatest weight gain and the lower feed conversion ratio. We found that as dietary cellulose and protein levels were increased, the activities of antioxidant enzymes (superoxide dismutase, catalase and glutathione peroxidase), immune response parameters (alkaline phosphatase, acid phosphatase, phagocytic index, respiratory burst, complement 3 and 4) and the mRNA level expression of copper/zinc superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase all rose. In contrast, rising cellulose levels were associated with decreased malondialdehyde contents and increasing tumour necrosis factor, interleukin 1 and interleukin 8 mRNA expression. Overall, our results indicate that dietary protein supplementation can enhance yellow catfish immune functionality and that while dietary protein impacts on the immune response are influenced by dietary cellulose levels, increased dietary cellulose was associated with inflammatory gene upregulation.