Stocking density and dietary inclusion of a multi-component functional feed additive on foot pad dermatitis, welfare indicators, and performance of broiler chickens.

This study evaluated the effects of stocking density (SD) and dietary supplementation of multi-component functional feed additives (PDS) on the performance and welfare-related indicators of broiler chickens. A total of 318 Ross 308 broilers, initial body weight 40.0± 0.9 g were assigned to five treatments: low stocking density (LD; 18 birds/m²), high stocking density (HD; 22 birds/m²), HD + 0.05% PDS (HD1), 0.075% PDS (HD2), or 0.10% PDS (HD3). Each treatment had six replicate pens and the trial lasted 35 d. Broilers under LD showed higher (p< 0.05) final body weight (BW), BW gain (BWG), and lower feed conversion ratio (FCR) than those reared under HD. Within the HD groups, increasing PDS supplementation improved final BW, BWG, and FCR through linear and quadratic responses (p< 0.05). Mortality rate during the finisher phase decreased linearly (p<0.05) with increasing PDS inclusion. High SD increased (p<0.05) FPD score, FPD occurrence, and the proportion of moderate-to-severe lesions, whereas PDS supplementation reduced FPD occurrence and shifted lesion distribution toward milder categories. Footpad appearance also improved progressively with increasing PDS inclusion. Birds under HD showed greater (p<0.05) C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-α), interleukin-1β (IL-1β), interleukin-10 (IL-10), and cortisol than those under LD. Supplementation with PDS resulted in linear reductions (p<0.05) in TNF-α, IL-1β, and cortisol, while CRP showed a tendency toward linear and quadratic responses. High SD increased (p< 0.05) fecal Salmonella, Clostridium, and Escherichia coli populations. Increasing PDS supplementation linearly reduced (p<0.05) Salmonella and Clostridium counts. In addition, HD increased litter moisture and ammonia concentrations compared with LD. In conclusion, high SD impaired broiler performance and welfare, as evidenced by lower growth performance, higher foot pad dermatitis, elevated stress and inflammatory markers, as well as increased pathogenic bacterial populations. Supplementation with PDS (0.05-0.10%) partially mitigated these responses and improved broiler resilience under high-SD.