The increasing concern over antibiotic growth promoters (AGPs) and the global rise in antimicrobial resistance have prompted the poultry industry to explore safer and more sustainable alternatives. Among these, postbiotics are non-viable microbial cells and/or their metabolic by-products along with non-nutritive feed additives such as organic acids, prebiotics, phytogenic compounds, and enzymes. These additives contribute to improved gut health by modulating the intestinal microbiome, enhancing immune function, and supporting overall physiological performance. This review critically evaluates the individual roles of postbiotics and non-nutritive feed additives in modulating poultry physiology and gut microbial ecology, while also integrating current evidence on their synergistic interactions. Particular emphasis is placed on combinatorial feeding strategies and their effects on microbial diversity, intestinal barrier integrity, pathogen suppression, and immune modulation. Recent advances in omics-based research are also discussed to provide mechanistic insights and highlight their implications for precision dietary formulation. Furthermore, current limitations and future research directions are outlined, including the need for standardized formulations, dose optimization, and large-scale field validation. Overall, postbiotics and non-nutritive feed additives represent promising next-generation tools for sustainable poultry production and for reducing antibiotic dependence in modern animal agriculture.

To Cite This Article: Li Z, Koka NA, Behan AA and Yang S, 2026. Synergistic effects of postbiotics and non-nutritive feed additives on poultry immune modulation and gut microbiome stability. Pak Vet J, 46(4): 746-758. http://dx.doi.org/10.29261/pakvetj/2026.089