Early-Life Intervention with Lactobacillus reuteri Enhances Intestinal2 Barrier Function and Resilience in Suckling Piglets via Modulation of3 Gut Microbiota and Metabolites

Early-life nutritional interventions are pivotal for promoting piglet growth and health, particularly in reducing weaning-associated disorders. This study investigated the effects of early-life Lactobacillus reuteri (L.reuteri) supplementation on growth performance, immune function, intestinal morphology, gut microbiota, ileal metabolites, and barrier function in suckling piglets. Neonatal piglets were administered L.reuteri for either 3 or 7 days post-birth. Results indicated that L.reuteri supplementation significantly increased weaning weight and average daily gain (ADG) while markedly reducing diarrhea incidence. Immune and antioxidant capacities were enhanced, evidenced by elevated serum and ileal IgG, IL-4, IL-10, T-SOD, T-AOC, and GSH-Px levels, alongside decreased pro-inflammatory cytokines (IL-1β, IL-6, TNF-α) and MDA. Histological analysis revealed improved intestinal architecture, characterized by increased ileal villus height and reduced crypt depth. 16S rRNA sequencing and metabolomic analyses showed that L.reuteri reshaped the gut microbiota by expanding beneficial Lactobacillus species and suppressing potential pathogens (Streptococcus, Pasteurellaceae), while modulating ileal metabolites involved in amino acid and energy metabolism. Multi-omics integration highlighted coordinated interactions between microbial composition and metabolites linked to improved health outcomes. Furthermore, the expression of tight junction proteins (Occludin, Claudin-3, ZO-1) and mucins (MUC-1, MUC-2) was significantly upregulated, indicating strengthened intestinal barrier integrity. Collectively, these findings demonstrate that early-life intervention with L.reuteri confers comprehensive benefits on suckling piglet health through immune enhancement, antioxidant protection, microbiota remodeling, metabolic regulation, and barrier reinforcement, supporting its potential as a practical strategy to improve early-life resilience and mitigate weaning-associated disorders in swine production.