Age-related changes in intestinal mucosal barrier function in laying hens during the mid-to-late production stages

Declining productivity in older laying hens is a major economic concern. In late-production stage hens, deterioration of the intestinal environment has been reported, suggesting that maintaining intestinal homeostasis is important for sustaining the productivity. As the intestine is vulnerable to pathogen invasion, a mucosal barrier is formed, consisting of microbiota and their metabolites, epithelial tight junctions, and immune cells in the lamina propria. However, the age-related changes in the intestinal mucosal barrier function during the mid-to-late production stages remain unclear. This study aimed to investigate age-related changes in intestinal mucosal barrier function during mid-to-late production stages of White Leghorn hens at approximately 300, 600, and 800 days old (n = 8 per group). Ileal and cecal mucosal tissues and luminal contents were collected to analyze tissue morphology, immune cell populations, cytokine and tight junction-related gene expression, antimicrobial peptides, IgA, short-chain fatty acids, and microbiota diversity. Subsequently, correlation analysis was performed between age-related factors that decreased with age and the bacterial abundance. With aging, the expression of cytokines involved in the differentiation and function of Th17 and Treg cells decreased significantly, particularly in the cecum. Moreover, the expression of tight junction-related genes and antimicrobial peptides was decreased. Correlation analysis identified bacterial groups showing positive or negative correlations with these age-related factors, suggesting the possibility of microbial regulation of Th17 and Treg cell-associated mucosal immunity. These findings suggest that microbial interventions targeting age-associated declines in Th17 and Treg cell functions may help preserve intestinal mucosal barrier integrity and ultimately support the maintenance of productivity in late-laying hens.