Dietary Effect of Probiotic Bacteria, Bacillus amyloliquefaciens-JFP2 on Growth and Innate Immune Response in Rock Bream Oplegnathus fasciatus, Challenged with Streptococcus iniae

The present study was conducted to evaluate the use of Bacillus amyloliquefaciens as a probiotic source in the diet of rock bream, Oplegnathus fasciatus. A total of 210 fingerlings (25.4 ± 0.13 g) were divided into two groups, three replicates each; control (C) and probiotic (P) group (35×3=105 fish per group). C group was fed a basal diet without probiotic while P group was fed with B. amyloliquefaciens spores at a concentration of 1.4 ×106 colony-forming units per gram (CFU/g) of feed. After 90 days, P group fish showed significant improvements in body weight (BW), weight gain (WG), specific growth rate (SGR) and food conversion ratio (FCR) when compared with C group fish. Also, in bi-weekly assessments, serum protein and glucose level showed a significant increase (p<0.05) in probiotic fed fish compared with the control group. Similar increase in serum antioxidant and lysozyme activity was found in the probiotic fed fish group. However, there was a significant decrease in triglyceride and total cholesterol along with increased alanine aminotransferase (ALT) and aspartate amonotransferase (AST) levels in probiotic diet fed fish compared to the control. After seventy days the fish were challenged with Streptococcus iniae and mortality of the probiotic fed fish was significantly lower (p<0.05) when compared with the control. These results demonstrate the benefit of incorporation of B. amyloliquefaciens as a feed supplement to improve the health status of Oplegnathus fasciatus challenged with Streptococcus iniae.