Effects of dietary antibiotic growth promoter and Saccharomyces cerevisiae fermentation product on production, intestinal bacterial community, and nonspecific immunity of hybrid tilapia (Oreochromis niloticus female × Oreochromis aureus male)1

Abstract

To investigate the effects of a dietary antibiotic growth promoter (florfenicol) and a Saccharomyces cerevisiae fermentation product (DVAQUA) on growth, G:F, daily feed intake, intestinal bacterial community, and nonspecific immunity of hybrid tilapia (Oreochromis niloticus ♀ × Oreochromis aureus ♂), a 16-wk feeding trial was conducted in a recirculating aquaculture system. Four feeding regimens were evaluated: control, dietary florenicol (0.02 g/kg; 16 wk), dietary DVAQUA (0.5 g/kg; 16 wk), and sequential use of florenicol (0.02 g/kg; 8 wk), and DVAQUA (0.5 g/kg; 8 wk). Each regimen had 4 replicate tanks (0.5 × 0.5 × 0.5 m) and each tank contained 12 fish (initial BW: 46.88 ± 0.38 g). Dietary florfenicol improved growth (P = 0.089), G:F (P = 0.036), and serum complement component concentrations (P < 0.001) of hybrid tilapia. However, the compound decreased the estimated intestinal bacterial count estimated by rpoB quantitative PCR (P < 0.001) and bacterial diversity (visual band numbers, Shannon diversity index, and Shannon equitability index based on 16S rDNA V3 denaturing gradient gel electrophoresis fingerprints) compared with the control. Although sequential use of florfenicol and DVAQUA improved growth and G:F numerically to a similar extent as dietary florfenicol, and increased intestinal bacterial count to normal quantities, the sequential use of florenicol and DVAQUA decreased intestinal bacterial diversity (visual band numbers, Shannon diversity index, and Shannon equitability index) as well as serum complement component concentrations (P < 0.001) compared with their respective use and the control. These findings might be negatively related to disease control and host defense, and the sequential use of florenicol and DVAQUA should be practiced with caution. Feeding DAVQUA to the fish improved nonspecific immunity and increased intestinal bacterial count and bacterial diversity, but further research, including challenge studies, should be conducted before recommendation of DVAQUA supplementation to hybrid tilapia diets.