The Role of Swine Gut Microbiota and Its Metabolites in Maintaining Intestinal Barrier Integrity and Mitigating Stress via the Gut–Brain Axis

The gut-brain axis is a complex communication network linking the gastrointestinal tract and the central nervous system, in which the gut microbiota plays a pivotal role in regulating intestinal homeostasis, immune responses and neuroendocrine functions. This review summarizes current knowledge on the role of the porcine gut microbiota in the functioning of the gut-brain axis and examines nutritional strategies aimed at its modulation. Key production-related stressors, such as weaning, transport and handling, disrupt microbiota composition, increase intestinal permeability and activate the hypothalamic-pituitary-adrenal (HPA) axis, leading to heightened stress responses, impaired immunity and behavioral disturbances. Evidence indicates that supplementation with probiotics, prebiotics, or postbiotics stabilizes the gut microbiota, enhances the production of bioactive metabolites, supports intestinal barrier integrity and alleviates oxidative stress. Such interventions improve adaptation to environmental stress, animal welfare and performance, while potentially reducing the need for antibiotics. Maintaining a balanced gut microbiota is therefore essential for the proper functioning of the neuroendocrine and immune systems in pigs. An integrated approach utilizing omics technologies (metagenomics, metabolomics, proteomics) may further elucidate microbiota-brain interactions and support the development of sustainable and ethical swine production strategies.