Multi-tissue transcriptomic profiling reveals the internal physiological landscape of laying hens in cage and cage-free systems

Welfare-friendly housing systems for laying hens, such as cage-free, have become prevalent. However, the physiological effects of housing systems on the laying hens remain poorly understood. Here, we compared behavioral characteristics and transcriptomic profiles from 90 multi-tissue samples among three housing systems: battery cage (BC), barn (BR), and free-range (FR). BR and FR housing promoted behavioral diversity compared to cages. Transcriptome analysis of central tissues (diencephalon and cerebral hemisphere) and peripheral tissues involved in egg production (liver, ovary, oviductal segments of magnum, and uterine) revealed significant enrichment of insulin resistance-related pathways in both diencephalon and liver of BC hens, and enhanced norepinephrine signaling in the cerebrum of BR and FR hens. To validate these findings, we performed a glucose tolerance test to assess insulin sensitivity and quantified the cerebral norepinephrine concentrations by ECD-HPLC. The results showed that BR and FR hens tended to exhibit higher insulin sensitivity and enhanced norepinephrine signaling compared with BC hens. Taken together, our findings suggest that housing conditions markedly shape the internal physiological landscape of laying hens, and also that environment-enriched cage-free contributes to improving metabolic and neurophysiological signaling.