Transcriptomic profiling of laying hen livers in relation to advanced ages and interaction with early life-rearing...

Extending hens' productive lifespan is a key goal for the layer industry to improve economic sustainability and reduce environmental impact. We investigated age-associated changes in hepatic gene expression in laying hens at conventional and extended culling ages, reared in floor or cage systems during early life, to assess how ageing affects liver transcriptome and how early-life rearing conditions interact with liver ageing. Using differential expression analysis, co-expression network analysis, and hierarchical clustering, we found that hepatic ageing was characterised by a transcriptional shift away from pathways related to lipid and cholesterol metabolism, bile acid synthesis, and lipid export, toward increased expression of genes involved in immune signalling, fatty acid oxidation, DNA damage response, and cellular stress responses, accompanied by a greater involvement contribution of regulatory long non-coding RNAs. This transcriptional shift metabolic decline was more pronounced in hens reared in cages than in floor systems. Older hens also displayed greater heterogeneity in their transcriptomic ageing trajectories, reflecting distinct patterns of metabolic and immune remodelling among individuals.