Exploring the supplementary effects of Saccharomyces boulardii and Bacillus subtilis B10 on broiler health as sustainable alternatives to antibiotics
For decades, the poultry industry relied heavily on antibiotics to promote growth and prevent disease in broiler chickens. However, with growing concerns about antibiotic resistance and consumer demand for cleaner food production, scientists have raced to find effective alternatives. The emergence of probiotic supplements represents one of the most promising solutions to this challenge—and the research behind them reveals a fascinating story of microbial allies working to enhance chicken health from the inside out.
Global efforts to reduce antibiotic use in animal agriculture due to resistance concerns.
Beneficial microorganisms offer sustainable alternatives for poultry health management.
At the forefront of this revolution are two remarkable probiotics: Saccharomyces boulardii (Sb), a beneficial yeast, and Bacillus subtilis B10 (Bs), a hardy bacterium. When supplemented in broiler diets, these microorganisms have demonstrated impressive abilities to improve digestion, boost immunity, and enhance overall health—all without the drawbacks of traditional antibiotics. The science behind how these probiotics accomplish this feat involves complex interactions with the chicken's gut environment, immune system, and even at the cellular level.
Saccharomyces boulardii is not your ordinary yeast. This unique strain has been extensively studied for its ability to support gastrointestinal health across multiple species. Unlike bacterial probiotics, being yeast-based gives Sb a significant advantage—it's naturally resistant to antibiotics that target bacteria, meaning it can be administered concurrently with necessary antibiotic treatments without losing effectiveness . This versatile probiotic performs multiple roles in the gut, from antimicrobial activity against pathogens to supporting the integrity of the intestinal lining and modulating immune responses .
Bacillus subtilis B10 belongs to a genus known for its remarkable resilience. These bacteria form protective endospores that allow them to survive harsh conditions, including the manufacturing process of feed pellets and the acidic environment of the digestive tract. This resilience ensures that Bs reaches the intestines alive and ready to colonize. Once established, it contributes to a healthy gut ecosystem through various mechanisms, including competition with harmful bacteria and production of beneficial compounds.
Together, these probiotics represent a powerful one-two punch against poultry health challenges, each complementing the other's strengths to provide comprehensive benefits throughout the digestive system.
To truly understand the impact of these probiotics, researchers conducted a comprehensive investigation into their effects on broiler chickens. The study employed rigorous scientific methodology to ensure reliable, actionable results that could inform poultry farming practices worldwide 1 3 5 .
The trial involved 300 one-day-old Sanhuang broilers, a Chinese cross-breed known for its quality meat production. These chicks were randomly divided into three experimental groups, each containing five replicates of 20 birds:
Received a basal diet supplemented with the antibiotic virginiamycin (20 mg/kg)
Received the same basal diet supplemented with Saccharomyces boulardii (1×10⁸ CFU/kg of feed)
Received the basal diet supplemented with Bacillus subtilis B10 (1×10⁸ CFU/kg of feed)
The supplementation continued for 72 days—covering the entire growth cycle of broiler chickens—after which samples were collected and comprehensive analyses were performed to evaluate various health parameters 1 .
| Group | Supplement | Dosage | Number of Birds | Duration |
|---|---|---|---|---|
| Control (CK) | Virginiamycin (antibiotic) | 20 mg/kg feed | 100 | 72 days |
| Sb Group | Saccharomyces boulardii | 1×10⁸ CFU/kg feed | 100 | 72 days |
| Bs Group | Bacillus subtilis B10 | 1×10⁸ CFU/kg feed | 100 | 72 days |
The research team observed significant improvements in key growth parameters among the probiotic-fed groups. Birds receiving either Sb or Bs showed increased live body weight and improved development of immune organs, as evidenced by the relative weight increase of the bursa of Fabricius and thymus—both critical components of the avian immune system 3 5 .
Average weight gain in probiotic groups
Villus height increase
Immune organ development
Perhaps even more impressive were the structural improvements observed in the digestive tract. Examination of intestinal tissues revealed that both probiotics led to:
The finger-like projections in the intestinal lining that absorb nutrients were significantly taller in probiotic groups, indicating a larger surface area for nutrient absorption
The villi were also broader, further enhancing their absorptive capacity
At the molecular level, researchers documented increased mRNA expression of proteins critical for maintaining intestinal barrier integrity, including occludin, claudin-2, and claudin-3. These "tight junction" proteins act like seals between intestinal cells, preventing harmful substances from leaking into the bloodstream while permitting nutrient absorption 3 .
The immunological benefits of probiotic supplementation proved equally remarkable. The Sb and Bs groups showed significantly increased IgA-positive cells in the jejunum, indicating enhanced mucosal immunity 3 . Furthermore, the probiotics modulated the expression of cytokines—key signaling molecules in the immune system—with observed increases in interleukin-6, tumor necrosis factor-α, interleukin-10, and transforming growth factor-β concentrations 3 5 .
The probiotics also influenced the innate immune system through activation of Toll-like receptors (TLRs), particularly TLR2, TLR4, and TLR15 in the jejunum and ileum. This activation triggered a signaling cascade involving MyD88, TRAF6, TAB2, and NF-κB—a pathway crucial for mounting appropriate immune responses against pathogens 6 .
| Parameter Category | Specific Improvements | Significance |
|---|---|---|
| Growth Performance | Increased live body weight | Better production outcomes |
| Improved immune organ development | Enhanced disease resistance | |
| Intestinal Health | Increased villus height and width | Enhanced nutrient absorption |
| More goblet cells | Improved mucosal protection | |
| Enhanced tight junction protein expression | Better gut barrier integrity | |
| Immune Function | Increased IgA-positive cells | Stronger mucosal immunity |
| Balanced cytokine production | Appropriate immune regulation | |
| Activation of TLR pathways | Improved pathogen recognition |
The researchers took their investigation a step further by analyzing how these probiotics influenced the broilers' gut microbiota—the complex ecosystem of microorganisms living in the digestive tract. Using advanced DNA sequencing technology, they discovered that the bacterial communities varied along different sections of the intestinal tract in the control and Bs groups, but remained more stable in the Sb group 1 .
The major bacterial phyla identified throughout the gastrointestinal tract included Firmicutes, Bacteroidetes, Proteobacteria, and Verrucomicrobia—microbes considered potentially related to growth performance. Importantly, Bacteroidetes, Proteobacteria, and Verrucomicrobia were present at much higher abundance in the jejunums and ileums of the Sb group, suggesting this probiotic created a more favorable microbial environment 1 2 .
The jejunal microbial communities formed three distinct clusters at both the genus level and in metabolic categories among the groups, based on principal component analysis. These findings indicate that Sb and Bs can effectively modulate the microbial ecosystem, creating conditions that support better health and growth in broilers 1 .
Understanding the tools and materials used in such experiments provides valuable insight into how nutritional research is conducted. The following table details some of the key reagents and solutions used in studying probiotic effects in poultry.
| Reagent/Material | Function in Research | Specific Application Example |
|---|---|---|
| Saccharomyces boulardii | Probiotic supplement | Cultured in YPD broth, added to feed at 1×10⁸ CFU/kg 6 |
| Bacillus subtilis B10 | Probiotic supplement | Cultured in LB broth, added to feed at 1×10⁸ CFU/kg 6 |
| Virginiamycin | Antibiotic control | Added to control group feed at 20 mg/kg as growth promoter comparison 1 |
| RNAiso reagent | Nucleic acid extraction | Isolating RNA from intestinal mucosal samples for gene expression analysis 6 |
| TLR and cytokine assay kits | Immune response measurement | Quantifying expression levels of Toll-like receptors and immune signaling molecules 6 |
| DNA Isolation Kit | Microbiome analysis | Extracting bacterial DNA from gut contents for microbiota profiling 1 |
The compelling evidence from this and similar studies paints a clear picture: Saccharomyces boulardii and Bacillus subtilis B10 represent viable alternatives to traditional antibiotics in poultry production. Their multifaceted benefits—spanning improved growth, enhanced intestinal structure, strengthened immunity, and optimized gut microbiota—demonstrate that we can maintain healthy, productive flocks without contributing to the global threat of antibiotic resistance.
Perhaps most importantly, these probiotics don't just replace antibiotics; they provide additional health benefits that extend beyond growth promotion to encompass overall animal wellbeing. As research continues to unravel the complex interactions between these beneficial microorganisms and their avian hosts, one thing seems certain: the future of sustainable poultry production will be increasingly fueled by probiotic power.
This research translates to potentially healthier poultry products and more sustainable farming practices.
It offers science-based tools to maintain flock health while meeting evolving market demands.
These advances mean living conditions that support their natural biology while promoting robustness and vitality.