Age-driven changes in the layer hen reproductive microbiome are associated with lay performance.

Eggs are a globally important food source and integral to optimal poultry production. Understanding the microbial ecology of the hen reproductive tract is essential for improving both food safety and reproductive efficiency. While the oviduct has been shown to harbor a continuous microbial community, this study is the first to demonstrate the presence of microbiota on the hen ovary surface, suggesting that the ovary is an extension of the oviductal microbial continuum. In this study, the ovarian and oviductal microbiomes of white-leghorn hens from mid-lay (high laying) and post-lay (lower laying) cohorts were analyzed. Using 16S rRNA sequencing, we identified significant shifts in reproductive tract microbiota between 9- and 18-month-old hens, coinciding with changes in lay performance. Several differentially abundant genera, including Acinetobacter, Ligilactobacillus, Bacillus, and Akkermansia, are known to modulate steroid hormone metabolism, with age-related abundance changes suggesting potential effects on hormone-driven reproductive processes. Other genera such as Ruminococcus_torques_group, Mucispirillum, and Fusobacterium-not traditionally associated with reproductive hormone pathways-may influence laying efficiency through their roles in mucin degradation, immune modulation, and inflammation. Notably, Turicibacter, newly identified on the ovary, increased with age and negatively correlated with lay performance, raising questions about its role in bile acid metabolism and stress response within the hen reproductive tract. Collectively, these findings highlight the ovary as an active microbial niche influenced by age and suggest that both hormone-associated and mucosal-interactive microbes contribute to lay dynamics. This work opens new avenues for probiotic strategies targeting key genera to support hen fertility and egg production across the productive lifespan.