ASSOCIATIONS BETWEEN ANIMAL WELFARE, GUT MICROBIOTA COMPOSITION, AND INTESTINAL INTEGRITY DURING WEANING IN PIGLETS.

Weaning represents a critical period in pig production, characterized by profound physiological, environmental, and nutritional challenges that can compromise intestinal health and animal welfare. Increasing evidence suggests that the gut microbiota plays a central role in mediating the response to these stressors, although its interactions with welfare-related factors under farm conditions remains incompletely understood. The aim of this study was to evaluate the relationship between animal welfare, gut microbiota composition, and intestinal integrity in weaned piglets under commercial conditions. Eight farms were assessed using standardized welfare indicators, and fecal samples were collected from piglets at weaning and 14 days post-weaning. Changes in microbiota composition were analyzed alongside markers of intestinal integrity and their associations with welfare parameters. Results showed that welfare-related factors were significantly associated with both intestinal integrity markers and microbiota composition. Improved environmental conditions, including space availability and pen management, were linked to reduced pro-inflammatory responses, as indicated by lower Interferon gamma (INF-γ) levels. Social behaviour was negatively associated with occludin expression, suggesting differences in epithelial barrier dynamics. Additionally, optimized feeding programs were positively correlated with Transforming growth factor beta (TGF-β) expression, indicating a more regulated immune environment. At the microbiota level, favourable welfare conditions were associated with increased abundance of fermentative and potentially beneficial taxa, including Ruminococcus, Eubacterium, Bacteroides, and Lactobacillus. These findings support the existence of a complex interaction between management practices, gut microbiota, and host physiology during the weaning period. Overall, this study highlights the importance of integrating welfare-oriented management and nutritional strategies to promote intestinal health and improve resilience to weaning stress in piglets.