Effects of Aging on the Microbiota and Inflammatory Status of the Intestinal and Oviductal Mucosa in Laying Hens

Abstract

Aging and inflammation of the intestinal and oviductal mucosa reduce egg production in laying hens. In mammals, microbiota changes in the intestine and reproductive mucosa are linked to aging and mucosal inflammation, but this relationship remains unclear in hens. The present study aimed to investigate the impact of aging on microbiota and inflammation in the intestinal and oviductal mucosa of hens. Sixteen White Leghorn hens aged ~280 days (young) and ~730 days (aged) were used. Bacterial DNA was extracted from feces and vaginal swabs for 16S rRNA amplicon sequencing. Intestinal (ileum and cecum) and oviductal (uterus and vagina) tissues were processed for histological analysis. Real-time PCR was performed to profile pro- and anti-inflammatory cytokines, tight junction-related molecules, and calbindin in the uterus. Whereas microbial diversity and composition in the vagina did not change with age; alpha-diversity of intestinal bacteria was lower in the aged group, as suggested by 46 genera showing a decrease and five an increase. The morphology of the ileum mucosa deteriorated, with transforming growth factor (TGF)β3 being upregulated and claudin (CLA)3 being downregulated in the intestine of the aged group. Finally, fibrosis progressed with age in the uterine mucosa, along with overexpression of IL-1β, TGFβ3, TGFβ4, and CLA1, but downregulation of calbindin in the oviductal mucosa. These results suggest that aging may impair intestinal and oviductal health through mucosal inflammation in both the intestine and oviduct of laying hens. This change may be related to alterations in the intestinal microbiota but appears less evident in the vagina.