Host-derived Bacillus-FOS synbiotic formulations improve growth performance and thermal stress resilience in juvenile olive flounder (Paralichthys olivaceus)
Dietary supplementation with host-associated Bacillus-FOS synbiotic formulations—particularly multi-strain combinations—favorably affected growth performance and lethal thermal challenge survival in juvenile olive flounder compared to unsupplemented controls.
| Outcome | Grade | Direction | Effect | Studies |
|---|---|---|---|---|
| Specific growth rate (SGR) | C | ▲ Favorable | Melhora significativa no grupo multiestirpe vs. controle; IC 95% não reportado | 1 |
| Lethal thermal challenge survival | C | ▲ Favorable | Superior nos grupos simbióticos multiestirpe vs. controle; IC 95% não reportado | 1 |
| Antioxidant enzyme activity (SOD, CAT) | C | ▲ Favorable | Modulação favorável nos grupos simbióticos; IC 95% não reportado | 1 |
| Heat-shock gene expression (hsp70, hsp90) | C | ▲ Favorable | Alteração significativa pós-desafio térmico vs. controle; IC 95% não reportado | 1 |
| Plasma immune-related indicators | C | ▲ Favorable | Modulação favorável nos grupos simbióticos; IC 95% não reportado | 1 |
| Intestinal morphology (villus height, crypt depth) | C | ▲ Favorable | Melhora histológica nos grupos simbióticos vs. controle; IC 95% não reportado | 1 |
| Feed conversion efficiency (FCE) | C | ▲ Favorable | Melhora significativa no grupo multiestirpe vs. controle; IC 95% não reportado | 1 |
Context
Olive flounder accounts for over 50% of Korean marine aquaculture production and faces increasing mortality risk from climate-driven heatwaves. Host-associated probiotics may offer better gastrointestinal compatibility than terrestrial strains, making Bacillus-FOS synbiotics a practical candidate for thermally stressed fish production systems. Evidence specific to host-derived formulations under lethal thermal stress in this species was previously lacking.
What the study showed
Multi-strain synbiotic groups showed statistically significant improvements in specific growth rate (SGR) and feed conversion efficiency versus control (exact absolute values and 95% CIs not consistently reported in available text). Lethal thermal challenge survival was higher in synbiotic groups, most notably multi-strain formulations. Antioxidant markers (SOD, CAT) and immune indicators were favorably modulated in treated groups. Expression of heat-shock genes (hsp70, hsp90) and energy-metabolism genes was significantly altered in synbiotic versus control groups following acute heat exposure.
How it was done
Controlled in vivo experimental study with juvenile olive flounder allocated to multiple dietary treatment groups (control plus single- and multi-strain Bacillus-FOS formulations). A feeding period preceded acute and lethal thermal challenge protocols. Growth, body composition, plasma biochemistry, intestinal histology, and gene expression were assessed. Strains were isolated from intestinal tracts of healthy wild olive flounder and identified by 16S rRNA gene sequencing.
Effect magnitude
Formal 95% confidence intervals for individual primary outcomes were not consistently reported. Statistically significant effects on SGR and lethal thermal challenge survival were demonstrated for multi-strain groups versus control; absolute effect sizes with confidence intervals require full numerical extraction from supplementary tables.
Limitations
Laboratory-scale study with aggregate sample size not clearly stated, limiting direct extrapolation to commercial aquaculture conditions. No formal risk-of-bias assessment tool (e.g., SYRCLE or ARRIVE guidelines) was reported. Strain identification relied solely on 16S rRNA sequencing, which has limited species-level resolution. Absence of post-intervention gut microbiota profiling prevents confirmation of the postulated colonization mechanism.
In clinical practice
Aquaculture nutritionists and farm managers may consider host-associated Bacillus-FOS synbiotic formulations as candidate functional feed additives for olive flounder under thermal stress risk. Commercial-scale validation under field temperature variability is required before formal recommendation. Evidence does not extend to other aquaculture species.
What is still missing
Commercial-scale field trials with gut microbiota monitoring, dose-response analysis of synbiotic formulations, and performance evaluation under real seasonal thermal variation are needed to support practical implementation.