Administration of Bacillus NP5 and Oligosaccharide to Enhance the Immune Response in Tilapia Oreochromis niloticus towards Streptococcosis

Abstract

Streptococcus agalactiae is a pathogen that causes streptococcosis which is becoming one of the major problems in tilapia culture. Application of probiotics, prebiotics, and synbiotics are expected to be an alternative in solving this problem by improving the immune response in tilapia. The aim of this study was to assess the effectiveness of Bacillus NP5 probiotic, oligosaccharide prebiotic and a combination of the two to stimulate the immune system for controlling S. agalactiae infection. The study consisted of five treatments with four replications, which were positive control P0 (+); negative control P0 (-); P1 (Bacillus sp NP5, probiotic 1%); P2 (oligosaccharide prebiotic 2%), and P3 (synbiotic: Bacillus sp NP5 probiotic 1% and oligosaccharide prebiotic 2%). The 15-20 g tilapia BEST strain was reared at a density of 10 fish per aquarium (60cm x 30cm x 40 cm). The administration of probiotic, prebiotic and synbiotic was applied for 14 days. On day 15, the fish were challenged by injecting of 0.1 ml S. agalactiae per fish at a concentration of 10⁵ CFU ml^-1, and then the fish were reared for 14 days and fed the control feed. The administration of probiotic, prebiotic, and synbiotic enhanced the immune responses and resistance to S. agalactiae bacterial infection in tilapia.

The results showed that the fish were given synbiotic treatment had the highest survival rate (83.34%) and better immune responses which was showed by a better erythrocytes, hemoglobin, hematocrit, total leukocyte, and phagocytic activity, than the positive control.