Synbiotic and postbiotic reuterin attenuate heat stress in rabbits by improving intestinal barrier function and modulating TLR4-NF-κB signalling.

Heat stress disrupts intestinal barrier integrity, immune homeostasis, and growth in rabbits, a species highly sensitive to thermal challenges. Microbiota-targeted interventions represent a potential strategy to mitigate these effects. This study evaluated the protective effects of a probiotic (Limosilactobacillus reuteri), a prebiotic (inulin), a postbiotic (reuterin), and a synbiotic (reuterin + β-galacto-oligosaccharides) under natural summer conditions. Rabbits (n = 6 per group) were assessed for thermoregulation, growth, intestinal barrier markers (jejunal zonula occludens-1 [ZO-1], plasma D-lactate), oxidative stress (malondialdehyde [MDA], superoxide dismutase [SOD], catalase [CAT], glutathione [GSH]), inflammatory signalling (TLR4-MyD88-NF-κB, TNF-α, IL-6, IL-10), and gut microbiota composition. All treatments improved thermoregulation, growth, barrier integrity, and redox balance, while suppressing pro-inflammatory signalling, with the synbiotic showing the most consistent benefits, including enrichment of beneficial microbes. In silico analyses indicated that inulin and reuterin interact with key immunoregulatory and metabolic proteins, supporting their functional bioactivity. Mechanistically, these interventions restore intestinal homeostasis by reshaping the microbiota, attenuating endotoxin-driven activation of the TLR4-MyD88-NF-κB axis, strengthening tight junctions, and enhancing antioxidant defenses, thereby reducing epithelial permeability and systemic inflammation. Synbiotic and reuterin-based treatments show the strongest effects, likely via synergistic modulation of host-microbe interactions and intracellular signalling pathways that stabilize barrier integrity, immune balance, and metabolic performance under heat stress.