In the present study, the evaluation of the welfare of broiler chickens reared in four different heating systems was assessed. The experiment was conducted in four aviaries with dimensions of 12 x 10m and 1000 birds each, at Embrapa Swine and PoultryFarm facilities, during four consecutive rearing cycles of 42 days. The heating systems evaluated were: a bio-fuel heater, a gas heater (GLP), a vegetable coal brick heater and a firewood heater. To assesses birds' welfare the following variables were obtained: heterophil/lymphocyte ratio (H/L), fluctuating asymmetry, foot pad assessment and gait score assessed by four gait scoring levels, 1- Regular (walk up 10 steps without limp or unbalance), 2- Impairment 1: walk up 10 steps and limping or unbalanced, 3 -Impairment 2: walk up four steps, limping or unbalanced gait 4 - remains still. All evaluations were performed when birds were 42 days-old. The birds had no foot pad lesions. Results from the fluctuating asymmetry test showed that birds were in a state of welfare. There's no effect of theheating treatments on gait score results. Between 95 to 97% of birds presented high level of welfare considering the locomotion stage exhibited during the experimental period. For the hematological evaluation, results showed that the number of heterophils increased and of lymphocytes decreased, thus changing the H/L ratio. This situation was consistent with the conditions of blood collection after routine management of birds, considered stressful. In conclusion, regardless the heating system applied, birds remained in good welfare conditions.
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