Abstract
Feather pecking remains one of the most critical behavioral and welfare challenges in free-range egg production systems, leading to plumage damage, increased mortality, and economic losses. This study evaluated the interactive effects of stocking density and environmental enrichment on feather pecking behavior, physiological stress indicators, and production performance in commercial free-range laying hens. A total of 1,200 Hy-Line Brown laying hens (20 to 40 weeks of age) were allocated to a 2 × 2 factorial design comprising two stocking densities (Standard: 9 hens/m² indoors, 4 m²/hen outdoors; High: 12 hens/m² indoors, 2 m²/hen outdoors) and two enrichment treatments (Control: standard wood shavings; Enriched: provision of lucerne bales, pecking blocks, and elevated perches). Severe feather pecking (SFP) acts were recorded bi-weekly, alongside plumage condition scoring, plasma corticosterone concentration measurements, and daily performance metrics. Enriched housing significantly reduced the frequency of SFP (P < 0.001) and plasma corticosterone concentrations (P < 0.01) across both stocking densities. High stocking density exacerbated feather damage and elevated stress hormone levels in non-enriched environments, whereas environmental enrichment successfully mitigated these negative outcomes. Hen-day egg production was highest (93.2%) and feed conversion ratio was optimal (2.04) in the low-density enriched group. These findings demonstrate that environmental enrichment acts as a crucial buffer against high-density stress, improving plumage condition, reducing physiological stress, and maintaining high laying performance in free-range systems.
