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.

The purpose of this study was to investigate the effects of chemically protected sodium butyrate (CSB) on growth performance and the early development and function of small intestine in broilers as one potential substitute for antibiotics. A total of 192 one-day-old Arbor Acres male broilers were randomly assigned into three dietary treatment groups (eight replicates per treatment): the control (CON) diet; ANT diet, CON diet supplemented with the antibiotics (enramycin, 8 mg/kg and aureomycin, 100 mg/kg); CSB diet, CON diet supplemented with 1000 mg/kg CSB, respectively. The results showed that dietary CSB and antibiotics addition significantly improved the growth performance of broilers by increasing the body weight gain (BWG) and feed conversion ratio (FCR) during different stages (p < 0.05). On day 21, the supplement of CSB in diet improved the structure of small intestine (duodenum, jejunum, and ileum) in broilers by increasing the ratio of villus height to crypt depth (VH/CD) (p < 0.05) and enhanced the butyric acid (BA) (p < 0.05) and total short chain fatty acids (SCFA) concentrations of small intestine (jejunum and ileum) compared with the CON and ANT diets. Besides that, the superoxide dismutase (SOD), total antioxidant capacity (TAC) and TAC to malondialdehyde (TAC/MDA) ratio of the ileal and jejunal mucosa were significantly higher (p < 0.05) in the CSB and ANT than in the CON. In addition, the supplement of CSB in diet markedly significantly enhanced α-amylase, lipase, and trypsin activities of the ileum (p < 0.05) as compared to the ANT diet. 16S rRNA gene sequencing indicated that CSB markedly increased the microbiota diversity of ileum in broilers at 21 days of age as compared to CON and ANT (p < 0.05). Furthermore, we found that Firmicutes was the predominant phyla and Lactobacillus was the major genus in the ileum of broilers. Compared with the ANT diet, the supplement of CSB in diet increased the relative abundance of some genera microbiota (e.g., Candidatus_Arthromitus, Romboutsia) by decreasing the relative abundance of Lactobacillus. Moreover, Akkermansia in the CSB was the highest in comparison to that in the CON and ANT. In addition, Kitasatospora that belongs to the phylum Actinobacteriota was only found in ileum of broilers fed the ANT diet. In summary, the supplement of 1000 mg/kg CSB in the diet improved the growth performance by promoting early development and function of the small intestine, which is associated with the regulation of intestinal flora and reestablishment of micro-ecological balance in broilers. Thus, CSB has great potential value as one of effective substitutes for in-feed antibiotics in the broiler industry.

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