Probiotics in Poultry: A Comprehensive Review of Mechanisms, Applications, and Future Directions.

Global poultry consumption continues to rise, while worldwide bans on in-feed antibiotic growth promoters raise an urgent requirement for eco-friendly alternatives to guarantee production efficiency and food safety. Probiotics, live beneficial microorganisms that improve host intestinal health, are reviewed. We elaborate four core functional pathways of probiotics: competitive exclusion of pathogens, enhancement of intestinal barrier integrity, immune modulation and regulation of microbial metabolites such as short-chain fatty acids. Their mitigating effects against heat stress, suboptimal rearing environments, mycotoxin contamination, heavy metal exposure and immune stress are analyzed. We further evaluate the capacity of single and compound probiotics to control major poultry diseases. Early-life intervention strategies and innovative preparations (multistrain probiotics, synbiotics, postbiotics) are systematically summarized. Critical bottlenecks restricting industrial translation are highlighted, including empirical strain combination, non-standardized administration protocols, divergent evaluation indicators and single-factor laboratory challenge models inconsistent with actual farm conditions. Finally, we propose future research directions covering multi-omics-assisted strain screening, optimized delivery technology, unified industrial quality control standards and field verification under compound stress. This review offers integrated references for mechanistic research, strain development and precise industrial application of probiotics in sustainable antibiotic-free poultry breeding.