Effects of Outdoor Stocking Density on Growth, Feather Damage and Behavior of Slow-Growing Free-Range Broilers

SIMPLE SUMMARY: Providing meat-type chickens free access to pasture is intended to improve their wellbeing by allowing them opportunities to express their natural behaviors and mitigate discomfort associated with indoor housing. However, there is limited information on how much pasture space is needed to improve the quality of life for these chickens. In a controlled experiment, chickens with a larger amount of pasture space had reduced feather damage and showed less aggression towards other chickens. Depending on age, chickens with a smaller amount of pasture space did more stretching, panting and sunbathing, which might be indicative displays of discomfort from being too hot. Regardless of the amount of pasture space that chickens had, they expressed an array of natural behaviors signifying that the small amount of pasture space provided for chickens did not hinder their welfare. Results of this study suggest that providing extra pasture space to chickens may improve their wellbeing. ABSTRACT: Access to pasture is a main benefit of free-range broiler housing systems, yet the level of outdoor stocking density on broiler animal welfare remains unsettled. The growth, feather damage, pasture ranging and behaviors were assessed for 150 mixed-sex, slow-growing Freedom Rangers from 5 to 11 weeks of age of with free access to either a high outdoor stocking density pasture (0.5 m(2) per bird) or a low outdoor stocking density pasture (2.5 m(2) per bird). The probability (mean, 95% CI) of tail feather damage was greater for the high-density (23.1%, 16.3 to 31.7%) compared to the low-density group (11.9%, 7.1 to 19.3%). The percent of observations resulting in sunbathing and aggressive attacks (i.e., pecking and fighting behaviors) were greater for the high-density (1.0%, 0.6 to 1.8% and 0.5%, 0.2 to 1.3%, respectively) compared to the low-density group (0.3%, 0.1 to 0.7% and 0.1%, 0.0 to 0.4%, respectively). Furthermore, an interaction between treatment and age indicated that birds in the high-density group displayed greater stretching (during weeks 7 to 10) and panting (during weeks 6 and 9). Results of this study suggest that additional outdoor pasture space may be positively associated with broiler welfare.