Rearing systems alter growth performance, behavior, brain characteristics, and meat quality in slow-growing Korat...

Alternative rearing systems have been increasingly adopted to improve poultry welfare and product quality. This study investigated the effects of organic (OR), free-range (FR), and conventional (CO) rearing systems on growth performance, behavior, brain characteristics, fatty acid profiles, and meat quality of slow-growing Korat chickens (KRC). A total of 375 mixed-sex day-old chicks were randomly allocated to 15 pens (5 replicates per treatment) and reared until 91 days of age. All birds were housed indoors at 5 birds/m², while FR and OR groups were provided access to Ruzi pasture at 1 and 4 m²/bird, respectively, from day 21. Behavioral activities were recorded by video observation during days 84 to 91. At slaughter, feather condition, brain structure, and meat quality were evaluated. Results indicated that OR chickens had significantly lower feed intake and final body weight compared with CO and FR birds (P < 0.05). Conversely, CO birds exhibited poorer feather condition, particularly in the tail region (P < 0.05). Principal Component Analysis (PCA) revealed distinct behavioral patterns among rearing systems, with CO birds displaying higher frequencies of aggressive behaviors (pecking, fighting), whereas FR and OR birds showed greater expression of nutritive and resting behaviors. Chickens reared under FR and OR systems exhibited lower brain porosity and greater brain volume compared with CO birds (P < 0.05). Regarding meat quality, FR and OR systems increased collagen content and shear force, while FR meat showed the lowest drip loss (P < 0.05). Moreover, the OR system significantly increased total n-3 polyunsaturated fatty acid (PUFA) content in breast meat (P < 0.05). Collectively, these results indicate that environmental complexity shapes brain integrity and behavioral resilience in KRC. This supports the adoption of welfare-oriented management practices, such as pasture access, to reduce aggression and improve meat quality. Such an approach may facilitate premium product differentiation, enabling producers to offset the economic constraints associated with slower growth rates through added welfare and nutritional value.