In October 2013, the International Scientific Association for Probiotics and Prebiotics (ISAPP) redefined the concept of probiotics, stating that probiotics are live microorganisms which, when administered in adequate amounts, confer a health benefit on the host. This definition has since become the global scientific consensus and serves as the foundation for regulatory frameworks and commercial applications in both human nutrition and animal husbandry.
Probiotics represent a broad category of beneficial microbes. Scientific research has consistently demonstrated that certain live microbial strains-when viable and delivered at effective dosages-can positively influence gut microbiota balance, enhance immune function, improve nutrient absorption, and suppress pathogenic bacteria in animals. As such, any microorganism meeting these functional criteria may be classified as a probiotic.
The majority of probiotic strains used in agriculture belong to Gram-positive bacteria, known for their safety profile and compatibility with digestive environments. The most commonly applied probiotics in livestock feed include:
Lactic acid bacteria (LAB)
Enterococci
Bacillus species
Selected yeast strains
Among these, lactic acid bacteria (LAB) are the most extensively studied and widely utilized group in animal feed production due to their natural presence in the gastrointestinal tract and fermented foods. Key LAB genera and species routinely incorporated into animal diets include:
Lactobacillus species:
Lactobacillus acidophilus (now often classified under Limosa or Apilactobacillus)
Lactobacillus casei
Lactobacillus plantarum
Lactobacillus fermentum
Lactobacillus delbrueckii subsp. lactis (formerly Lactobacillus lactis)
Lactobacillus delbrueckii subsp. bulgaricus (formerly Lactobacillus bulgaricus)
Lactobacillus reuteri
Pediococcus species:
Pediococcus acidilactici
Pediococcus pentosaceus
Enterococcus species:
Enterococcus faecalis
Enterococcus faecium
Enterococcus lactis
Despite their proven benefits in modulating intestinal flora and improving feed efficiency, many lactic acid bacteria exhibit limited environmental stability. They are generally sensitive to heat, oxygen, gastric acid, and bile salts, resulting in poor survival during feed processing (especially pelleting), storage, and passage through the upper digestive tract. To overcome this limitation, advanced formulation technologies-such as microencapsulation, cryoprotection, freeze-drying, and matrix embedding-are employed to protect cell viability and ensure sufficient live delivery to the target site in the gut.
As of June 2025, the Ministry of Agriculture and Rural Affairs of China (MARA) has officially approved the following microbial strains for use as feed additives, categorized by permitted application scope:
✅ Approved Microbial Strains in China's Feed Additive Catalog (Updated June 2025)
1. General Use Across Livestock, Poultry, Aquaculture, Companion Animals (Dogs & Cats):
These strains are cleared for broad inclusion in compound feeds and premixes for multiple animal species, including pigs, poultry, ruminants, fish, shrimp, dogs, and cats.
Bacillus licheniformis
Bacillus subtilis
Bifidobacterium bifidum
Enterococcus faecalis
Enterococcus faecium
Enterococcus lactis
Lactobacillus acidophilus
Lactobacillus casei
Lactobacillus delbrueckii subsp. lactis (previously L. lactis)
Lactobacillus plantarum
Pediococcus acidilactici
Pediococcus pentosaceus
Candida utilis (produces microbial protein)
Saccharomyces cerevisiae (brewer's or baker's yeast)
Rhodopseudomonas palustris (photosynthetic bacterium, supports pond ecology)
Bifidobacterium infantis
Bifidobacterium longum
Bifidobacterium breve
Bifidobacterium adolescentis
Streptococcus thermophilus
Lactobacillus reuteri
Bifidobacterium animalis
Aspergillus niger (enzyme-producing mold, aids fiber breakdown)
Aspergillus oryzae (used in fermentation and enzyme synthesis)
Bacillus lentus
Bacillus pumilus
Lactobacillus cellobiosus
Lactobacillus fermentum
Lactobacillus delbrueckii subsp. bulgaricus
🔍 Note: Several taxonomic updates reflect current phylogenetic understanding. For example, some Lactobacillus species have been reclassified into novel genera based on whole-genome analysis (e.g., Limosilactobacillus, Ligilactobacillus), though they remain functionally recognized as probiotics.
2. Approved for Silage and Ruminant Feeds (e.g., Dairy/Beef Cattle):
These strains promote efficient ensiling by accelerating lactic acid production, reducing pH rapidly, and inhibiting spoilage organisms.
Propionibacterium acidipropionici – enhances propionic acid formation, improves aerobic stability of silage
Lactobacillus buchneri – extends shelf life of silage by suppressing yeast growth and minimizing heating during feed-out
🧪 Practical Impact: Inclusion of Lb. buchneri reduces dry matter loss by up to 30% during prolonged exposure to air, making it essential for modern high-moisture corn and alfalfa silage management.
3. Specifically Approved for Silage Only:
Lactobacillus paracasei – contributes to rapid acidification and stable fermentation in forage preservation
4. For Broilers, Grower-Finisher Pigs, Aquatic Species, Dogs, and Cats:
Bacillus coagulans – spore-forming lactic acid producer with strong thermal and gastric resistance; highly stable in pelleted feeds
Unique advantage: Survives industrial processing without encapsulation, colonizes transiently, produces lactic acid and antimicrobial compounds
5. For Broiler Chickens, Ducks, Swine, and Shrimp:
Brevibacillus laterosporus (formerly Bacillus laterosporus) – exhibits dual activity: probiotic support and biocontrol against pathogens like E. coli and Vibrio spp. in aquaculture
Known for producing unique lipopeptides with antifungal and antibacterial properties
6. Exclusively Approved for Broiler Chickens:
Bacillus velezensis – emerging star in sustainable poultry production
Produces a suite of bioactive metabolites (surfactins, iturins, bacillomycins) that inhibit Clostridium perfringens, Salmonella, and Campylobacter
Enhances villi development and nutrient digestibility
Gaining traction as an antibiotic growth promoter (AGP) alternative
🌱 Strategic Role of Probiotics in Modern Sustainable Animal Production
With increasing global pressure to reduce antimicrobial use in livestock, probiotics have evolved from niche supplements to core components of health-oriented, antibiotic-free feeding programs. Their mechanisms extend beyond simple microbial replacement-they actively shape host physiology through:
Gut Barrier Enhancement: Upregulation of tight junction proteins (e.g., occludin, ZO-1), reducing "leaky gut" syndrome.
Immunomodulation: Stimulation of secretory IgA, modulation of T-regulatory cells, and balanced cytokine responses.
Competitive Exclusion: Occupation of adhesion sites and production of bacteriocins that inhibit pathogens.
Metabolic Contributions: Synthesis of vitamins (B-group, K), short-chain fatty acids (SCFAs), and improved nitrogen utilization.
Stress Mitigation: Alleviation of heat stress, weaning stress, and transport-related dysbiosis.
Moreover, the integration of multi-strain consortia-combining lactic acid producers, spore-formers, and yeasts-is now considered best practice. Such synergistic blends offer broader ecological coverage across gut regions and greater resilience under variable conditions.
🔬 Regulatory Alignment & Market Implications
China's MARA-approved list reflects a science-driven, risk-assessed approach aligned with international standards set by EFSA (European Food Safety Authority), FDA (USA), and FAO/WHO guidelines. Each listed strain must undergo rigorous evaluation for:
Species-level identification (via 16S rRNA + whole-genome sequencing)
Absence of transferable antibiotic resistance genes
Toxicity and pathogenicity screening
Stability and efficacy data under real-world conditions
This regulatory clarity not only ensures product safety but also fosters innovation in precision fermentation, strain selection, and targeted delivery systems.