Inter-Observer Repeatability of Indicators of Consciousness after Waterbath Stunning in Broiler Chickens

SIMPLE SUMMARY: Waterbath stunning is intended to induce unconsciousness until death occurs due to bleeding in poultry. However, it is not always effective. For this reason, in order to protect their welfare, it is mandatory in the European Union that the state of consciousness of broiler chickens is monitored at the exit of the waterbath, and that they do not regain consciousness before death. Ineffectively stunned birds can be re-stunned using back-up methods to avoid unnecessary pain, stress and suffering. One of the main challenges in monitoring the state of consciousness in broiler chickens after waterbath stunning is the selection of animal-based indicators ensuring consistency among assessments. The indicators should be valid, feasible and repeatable. However, only the validity and feasibility have been reported. Thus, the main goal of this research was to assess the repeatability of the most valid and feasible indicators of the state of consciousness after waterbath stunning in broilers both before bleeding (tonic seizure, breathing, spontaneous blinking and vocalization) and during bleeding (wing flapping, breathing, spontaneous swallowing and head shaking). This study proposes a refined list of indicators that could be used to assess the consciousness of broiler chickens in commercial slaughterhouses. ABSTRACT: This study evaluated the prevalence and tested the inter-observer repeatability of the most valid and feasible animal-based indicators of the state of consciousness after waterbath stunning in broilers before bleeding (tonic seizure, breathing, spontaneous blinking and vocalization) and during bleeding (wing flapping, breathing, spontaneous swallowing and head shaking). In addition, correlations among them were computed to better understand their relationship and offer insights into the reliability of such indicators. This was aimed at proposing a refined list of indicators that could be used in commercial slaughterhouses to ensure consistent assessments. This study compared the assessments of three observers of 5241 broilers from 19 batches in six different slaughterhouses. Inter-observer repeatability was assessed through the combination of the crude percentage of agreement and the Fleiss’ kappa coefficient and interpretation. Before bleeding, the results led us to recommend assessing breathing over spontaneous blinking and vocalizations and to neglect tonic seizure in commercial conditions. During bleeding, the recommended indicators are breathing, wing flapping and head shaking while spontaneous swallowing can be neglected.