By taking a step-by-step approach to the design process and by learning how fo manipulate the behavioural and physical characteristics of broilers, researchers in Georgia, USA, have made considerable progress. Broiler chickens slaughtered at commercial processing plants typically are hung upside down on moving shackle lines that take them through the various steps of first processing. The hanging is done by teams of people who must pick live birds up from the conveyor or crate, reorient them and quickly force the shanks of the legs down into a passing shackle. Typically, eight workers hang 180 broilers every minute or one bird every 2.5-3.0 seconds for each worker. The work is physically demanding and repetitious, creating the risk of repetitive motionrelated injury. Continuous exposure to the airborne dust raised by the wing flapping of birds can promote allergic reactions and respiratory illness. The work environment is often noisy and dark. As a result, its hard to find reliable, conscientiousindividuals to do the work. Rough handling of the broilers causes fear, struggle and sometimes injury to the bird. Human error is unavoidable, thus occasionally a bird is hung by one leg or backward, or even a dead bird is hung. For years, the broiler industry has wanted to improve the shackling process. Gas killing systems solve some of the problems but still require repetitious labour.
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