Effects of stocking density and string provision on welfare-related measures in commercial broiler chickens in windowed houses

Abstract

Lower stocking densities (SD) are sometimes used in windowed houses for broilers as part of systems designed to produce high-welfare products. However, there is little scientific information on the effects of SD on welfare-related measures in broilers in windowed houses, and on whether these effects are influenced by environmental enrichment. Commercial windowed broiler chicken houses were assigned to 4 target SD (30, 32, 34, and 36 kg/m2) and 2 levels of access to string [+S (one piece per 1,000 birds/house), -S] in a 4 × 2 factorial arrangement. Treatments were applied in one of 4 houses on each of 2 farms, and replicated over 10 production cycles. Levels of lying behavior, apparent fear-related behavior, and gait score were observed in wk 3 to 5. The incidence and severity of dermatitis lesions were assessed at d 30 and at slaughter. Environmental and production performance parameters also were measured. No significant treatment effects were obtained for levels of lying or fear-related behavior, final body weight, presence of dermatitis lesions at slaughter, or percentage of downgraded carcasses. There were no significant treatment effects on measures of gait, but the percentage of birds with a gait score of ≥2 tended to increase at higher SD. The severity of dermatitis lesions at d 30 increased with increasing SD, and was significantly greater at densities of 34 and 36 kg/m2 than of 30 kg/m2. Litter moisture content was not significantly affected by treatment, which may have reflected a numerical decline in water consumption with increasing SD. Results suggest that increasing SD is a risk factor for more severe dermatitis; however, increasing density from 30 to 32 kg/m2 did not significantly affect this variable. In addition, the proportion of lame birds, levels of lying behavior, and performance were not significantly affected by increasing SD. Providing suspended string at typical commercial levels did not have beneficial effects on welfare-related measures, and further research should perhaps investigate effects of greater levels of provision.