The impact of laying hen housing systems on egg production, egg quality, and intestinal microbiota of the hens

The global transition toward cage-free egg production has intensified discussions about how different housing systems affect egg production, egg quality, and the intestinal microbiota of laying hens. This review synthesizes current scientific findings on conventional cages, free-range, cage-free, and organic egg systems, highlighting their influence on hen productivity, egg characteristics, and gut microbiota composition. While conventional systems often promote higher early productivity and improved eggshell integrity, alternative systems tend to support better welfare, more sustained production over time, and, in some cases, enhanced internal egg quality. However, inconsistencies across studies reflect the influence of various interacting factors such as genetics, nutrition, environmental conditions, and management practices. Moreover, housing systems significantly affect gut microbiota diversity and composition, with notable implications for nutrient absorption, egg quality, and host health. These findings underscore the complexity of balancing animal welfare, sustainability, and productivity in modern egg production and emphasize the need for integrated approaches considering not only biological outcomes but also socio-economic and legislative contexts.