AUTHOR=Panase Arporn , Thirabunyanon Mongkol , Promya Jongkon , Chitmanat Chanagun 

TITLE=Influences of Bacillus subtilis and fructooligosaccharide on growth performances, immune responses, and disease resistance of Nile tilapia, Oreochromis niloticus

JOURNAL=Frontiers in Veterinary Science

VOLUME=9

YEAR=2023

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2022.1094681

DOI=10.3389/fvets.2022.1094681

ISSN=2297-1769

ABSTRACT=<p>The present study investigated the effects of <italic>Bacillus subtilis</italic> and fructooligosaccharide (FOS) on growth performances, immunity improvement, and disease resistance of Nile tilapia (<italic>Oreochromis niloticus</italic>). The fish (24.5 ± 1.6 g) were fed a basal diet (G1), diets supplemented with 1 g/kg (G2), 3 g/kg (G3) and 5 g/kg (G4) of FOS as well as diets supplemented with 1 × 10<sup>9</sup> CFU/g (G5), 3 × 10<sup>9</sup> CFU/g (G6) and 5 × 10<sup>9</sup> CFU/g (G7) of <italic>B. subtilis</italic> for 56 days. After the feeding trial, the complement C3, <italic>IL-1</italic>β, <italic>TNF-</italic>α, IFN-γ, <italic>hsp70</italic> gene expression in the liver was then analyzed by a quantitative Real-time PCR. Then, fish were infected with <italic>Streptococcus agalactiae</italic>, and the survival rate was recorded. The results showed that FOS and <italic>B. subtilis</italic> had no significant effect (<italic>P</italic> &gt; 0.05) on growth performances and survival rate. Lysozyme activity was significantly greater in the G4, G5, G6, and G7 groups. Also, all fish fed FOS and <italic>B. subtilis</italic> showed significantly (<italic>P</italic> &lt; 0.05) higher respiratory burst activity than other groups. The expressions of complement <italic>C3, IL-1</italic>β, <italic>TNF-</italic>α, <italic>IFN-</italic>γ, and <italic>hsp-70</italic> in the liver were significantly higher for fish fed 5 g/kg of FOS as well as for fish that received any concentration level of <italic>B. subtilis</italic> (<italic>P</italic> &lt; 0.05) used in the study. After the <italic>S. agalactiae</italic> challenge test, the survival rate of fish-fed diets supplemented with FOS and <italic>B. subtilis</italic> was slightly higher than for the control group. The results indicated that FOS an<italic>d B. subtilis</italic> could stimulate immune responses and immune-related genes in tilapia. However, further investigation of other prebiotics or herbs in combination with <italic>B. subtilis</italic> is encouraged at molecular levels and screening for beneficial metabolites that may increasingly improve digestive enzymes, growth performances, and health benefits in tilapia. In addition, on-farm experiments are needed.</p>