Next-Generation Probiotics in Poultry: From Conventional Strains to Engineered and Synbiotic Approaches.

The global poultry industry faces a major transition driven by bans on antibiotic growth promoters (AGPs) and rising antimicrobial resistance threats. This has intensified the search for effective, sustainable alternatives to maintain productivity, animal health, and food safety. This review provides a comprehensive overview of next-generation probiotics (NGPs) and their evolving role in poultry production, highlighting their mechanisms of action, technological advancements, and applications for improving performance and health. Recent studies were systematically reviewed, covering conventional and NGPs, multi-omics-driven strain identification strategies, engineered microbial systems, and advanced delivery technologies. Key functional aspects, including gut microbiota modulation, immune responses, pathogen control, and productivity metrics were thoroughly assessed. NGPs exhibit enhanced capabilities over traditional probiotics, including improved gut colonization, targeted antimicrobial activity, and precise host immune modulation. Advances in synthetic biology, microencapsulation, and synbiotic formulations enhance their efficacy and stability. Additionally, NGPs also demonstrate significant potential in improving growth performance, feed conversion ratios, intestinal integrity, and enteric pathogen resistance. However, challenges such as strain-specific variability, regulatory constraints, and limited field-level validation persist. NGPs offer a promising and sustainable strategy for modern poultry production. Future integration with precision microbiome engineering, artificial intelligence, and sustainable farming will be essential to realize their full potential and ensure widespread adoption.