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Wolff, Inga; Klein, Sandrina; Rauch, Elke; Erhard, Michael; Moench, Julia; Haertle, Sonja; Schmidt, Paul and Louton, Helen (2019): Harvesting-induced stress in broilers: Comparison of a manual and a mechanical harvesting method under field conditions. In: Applied Animal Behaviour Science, Vol. 221, 104877

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Harvesting of broilers is a stressful event, whether done mechanically or manually. The use of harvesting machines might compromise animal welfare less than manual harvesting methods because it is less influenced by environmental and flock-specific factors. In this paper, a mechanical and a manual harvesting method are compared in regard to stress-induced behavioural and physiological reactions. The stationary person test and the avoidance distance touch test were applied before harvesting to estimate pre-treatment fear of humans in the flocks. We then recorded the behaviour of the flocks during harvesting and evaluated stress-induced behaviour such as wing flapping and escape behaviour. Furthermore, we took blood samples at the abattoir and analysed the corticosterone concentration and heterophil/lymphocyte ratio. In a statistical analysis, all assessed parameters were related to environmental and flock-specific factors, as well as to the risk of lesions such as haematomas and fractures. Our aim was to figure out if the use of a harvesting machine, in this case the Apollo Generation 2, puts less stress on broilers during harvesting than manual catching. The applied behaviour tests indicate the excitability and fear of humans of the flocks but are complex to interpret. Compared with mechanical harvesting, manual harvesting was more influenced by environmental and flock-specific factors such as average weight (odds ratio [OR] = 1.49;95% confidence interval [CI] [1.11;2.22]) or catching duration (OR = 1.79;95% CI [1.44;2.19]). The results verified a correlation between stress-induced behaviour and the occurrence of lesions. The risk for haematomas was influenced by escape behaviour during manual harvesting (OR = 1.07;95% CI [1.02;1.13]) and by bumps against the containers (OR = 1.06;95% CI [1.05;1.07]) and flips (OR = 6.23;95% CI [3.99;9.27]) during mechanical harvesting. The risk for fractures during mechanical harvesting was influenced by the occurrence of flips (OR = 2.74;95% CI [1.07;5.67]). The risk for wing flapping was twice as high during manual harvesting as during mechanical harvesting (OR = 2.11;95% CI [1.82;2.44]). The blood parameters showed no correlations with the initial behaviour test results and the assessed stress-induced behaviour during harvesting. Corticosterone concentration was strongly influenced by light intensity (beta = 3.75;95% CI [2.55;4.95]) and outdoor temperature (beta = 46.34;95% CI [39.18;53.27]) during manual harvesting. The results showed weak points of both harvesting methods, and we offer suggestions to improve animal welfare during harvesting.

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