Comparative immunostimulatory effect of probiotics and prebiotics in Channa punctatus against Aphanomyces invadans.

In aquaculture and human health care probiotics and prebiotics have been widely used due to their important role in enhancing beneficial gut microbiota, promoting growth, increasing disease resistance, and positively modulating the host immune system. This study reports for the first time a comparative analysis on the effect of the probiotics and prebiotics on growth, digestive enzymes activity, antioxidant activity, and immune response in Channa punctatus against Aphanomyces invadans. Among the diets enriched with Saccharomyces cerevisiae (S. cerevisiae) and Galactooligosaccharide (GOS) in C. punctatus, feeding 2.5 g kg diet did not significantly influence the mean weight gain (MWG) between weeks 2 and 4 in both the infected and control groups; however the increase in MWG became significant from weeks 6-8. Similarly, during this period the protein efficiency ratio (PER), feed conversion ratio (FCR) and protein intake (PI) did not increase significantly. The intestinal protease, lipase, and amylase enzyme activities also did not increase significantly between weeks 2 and 4, whereas the values increased significantly after 6 weeks in both groups when fed with dietary supplementation of S. cerevisiae and GOS. The total S. cerevisiae count significantly increased in the gut of infected and non-infected fish fed with S. cerevisiae and GOS diets while the total bacterial (TB) count decreased between weeks 6 and 8. The total superoxide dismutase (t-SOD) activity and the malonaldehyde (MDA) concentration increased significantly in the non-infected fish fed with S. cerevisiae and GOS supplementation diets between weeks 6 and 8 whereas the catalase (CAT) and glutathione peroxidase (GPx) activities increased significantly only on week 8. The innate immune parameters such as plasma lysozyme, acid phosphatase (ACP), and myeloperoxidase (MPO) activities increased significantly in the infected and non-infected fish fed with S. cerevisiae and GOS containing diets after 6 weeks. Similarly, the plasma nitric oxide (NO) level and total protein (TP) content significantly increased in the non-infected fish fed with S. cerevisiae and GOS containing diets between weeks 6 and 8. In the control and the non-infected fish fed with S. cerevisiae and GOS enriched diets caused no mortality whereas 15% and 10% mortality was observed in the infected fish fed with S. cerevisiae and GOS diets, respectively. This study indicates that the infected and non-infected C. punctatus fed with dietary supplementation of GOS diet at 2.5 g kg had exhibited better growth performance, digestive enzyme activities, gut microbiota composition, and immune response than that of S. cerevisiae diet.