Welfare of broiler chickens reared in two different industrial house types during the winter season in Southern Brazil.

1. The following trial compared broiler chicken welfare in closed-sided (CS) open-sided (OS) industrial house types during the winter season in the South of Brazil.2. Ten flocks in each house type were evaluated as follows: a) bird health: contact dermatitis on the breast and abdominal areas (CDE), bird soiling (BSO), footpad dermatitis (FPD), hock burn (HBU), lameness (LAM), fractures (FRA), bruising (BRU), scratches (SCR), dead on arrival (DOA), and diseases (DIS); b) house environmental measurements: relative humidity (RHU), temperature (TEM), air velocity (AVE), illuminance (ILL), ammonia concentration (NH), and carbon dioxide concentration (CO), and c) bird behaviour and affective states: bird behaviour (BBE), touch test (TTE), and qualitative behaviour assessment (QBA).3. Statistical analyses were based on regression models for CDE, BSO, FPD, HBU, LAM and generalised linear models for DOA, FRA, BRU, SCR, and DIS. The Mann-Whitney test was used for RHU, TEM, AVE, ILL, NH, CO, and the t-test for TTE and LMO, with a specific regression model for BBE data and Principal Component Analysis for QBA.4. According to odds ratio for worse scores for CS relative to OS, birds were less likely to have severe scores for CDE (P = 0.040 and P = 0.007), BSO (P = 0.031, P = 0.016, and P = 0.038), and HBU (P = 0.017), and had higher median values for AVE (2.3, 0.0-7.8 m s . 0.0, 0.0-4.3 m s), lower NH concentration (9.0, 0.0-64.0 ppm . 12.0, 0.0-60.0 ppm) and TTE scores (98, 96-100 . 67, 25-100). Worse results were observed in CS houses for higher stocking density (13.8 ± 0.2 birds/m . 12.0 ± 0.2 birds/m), RHU (74.5, 50.7-99.9% 72.3, 47.4-99.9%), and TEM (23.9, 14.6-29.2°C . 21.7, 12.9-30.1°C), lower ILL (16.0, 1.0-60.0 lx . 161.0, 8.0-2380.0 lx), less drinking (P = 0.007), more inactive behaviour (P < 0.001) and lower positive emotions, according to QBA (P = 0.028).5. In the studied region and season, CS houses seemed to offer fewer welfare problems in terms of the health indicators; however, OS houses showed fewer behavioural restrictions and higher positive emotional states.