The objective of this study was to investigate if blue lighting could reduce broiler stress and comply with legal labor comfort requirements in a new shackling area of a middle-size processing plant. In this study, the old shackling area was compared with the new area, where a blue lighting system was designed and implemented according to the regulations. The old and new areas were video-and audio-recorded during the shackling of 33,850 broilers in each area. Data were statistically analyzed using the non-parametric test of Wilcoxon-MannWhitney (w test).The results indicated 56% reduction in wing-flapping and 3.2% noise reduction in the new area. These results were obtained by increasing 119% lighting at the work stations in the shackling area, allowing workers to handle the birds more carefully, which may improve processing plant productivity. The study demonstrated that it is possible to conciliate better animal welfare with visual comfort for workers in the shackling area.

Keywords Broilers, animal welfare, electric stunning by electronarcosis, stunning severity index, Statistical Process Control, control charts. ABStRACtThe objective of this study was to evaluate the efficiency of electrical stunning by electronarcosis in a medium-size poultry processing plant located in southern Brazil. The current measurement of this type of stunning is presented, and then improvements to this method are proposed. Data were collected for 90 days. A quality indicator was proposed: the Stunning Severity Index (SSI), which includes elements of Statistical Process Control (SPC) using a p-chart (proportion chart) and measures. This index comprises the variables "wing-flapping," "arched head," and "rhythmic breathing." Using the proposed index, 5% of the birds, on average, presented inefficient stunning symptoms.