Effect of free-range access, shelter type and weather conditions on free-range use and welfare of slow-growing broiler chickens

Free-range access for broiler chickens can benefit animal welfare because the birds have access to a more natural environment and more opportunities to perform natural behaviours than in indoor systems. Also, they have more space and more environmental enrichment, which could lead to better leg health and decreased fearfulness. In practice, however, use of the free-range area is often low. Lack of shelter likely plays an important role in this, as do weather conditions. In this study during 2 production rounds of slow-growing broiler chickens, 200 chickens were housed indoors (IN), 200 were provided with free-range access to grassland with artificial shelter (AS), and 200 were provided with free-range access to an area with short rotation coppice (SRC) from 4 until 10 weeks of age. Free-range use was monitored using photographs and live observations. Weather conditions and free-range use were monitored throughout the outdoor period. Tonic immobility (TI) as fearfulness assessment was done at the beginning (round 2 only) and the end of both production rounds; leg health and tibia bone health were assessed at the end of the production rounds. Mean percentage of birds using the free-range area was higher in SRC than in AS groups (42.8% vs. 35.1%; F1,7 = 1180.00, P < 0.001). The mean percentage of animals located further than 5 m from the house was 10.6 ± 1.1% of the chickens that were outside in the SRC groups vs. 4.1 ± 0.8% in the AS groups (F1,7 = 24.03, P = 0.002). The interactions of shelter type with rainfall (F2,5578 = 70.59, P < 0.001), increasing radiation (F2,5578 = 300.93, P < 0.001) and increasing wind speed (F2,5578 = 14.77, P < 0.001) showed that these factors were related with fewer chickens being outside; and that these effects were more pronounced in SRC than in AS chickens. An increasing temperature was related with more free-range use (F1,5578 = 32.24, P < 0.001). A shorter TI duration in week 3 (at group level) was associated with more chickens further than 5 m from the house (F1,250 = 13.79, P < 0.001). The percentage of animals needing more than one induction to induce TI in week 10 was higher for chickens from SRC (29.7%) than from IN groups (4.8%; t102 = −2.61, P = 0.028) but not AS (14.8%). Hock dermatitis occurred less in AS (7.6%) than in IN (40.1%; t222 = 3.15, P = 0.005) but not SRC (13.7%). These findings indicate that presence of SRC was most effective in encouraging chickens to use the free-range area, but that free-range access was only moderately related to better leg health and fearfulness (at group level).