Relevant Indicators of Consciousness after Waterbath Stunning in Turkeys and Stunning Efficiency in Commercial Conditions

Simple Summary Multi-bird waterbath stunning (WBS) is the main commercially used stunning method in poultry. However, not all birds are unconscious after WBS and some of them recover consciousness before death due to differences in individual bird's resistance to electricity. In order to minimize pain, distress and suffering of ineffectively stunned turkeys, operators must be trained to identify indicators of consciousness so they can re-stun the birds using backup methods. However, the literature reflects that there is no standardization in the applied indicators. In this sense, the prevalence of detected conscious birds can be biased according to the indicators chosen. Relevant indicators must be valid, feasible and repeatable. The validity and feasibility of indicators of the state of consciousness in poultry have been reported by the EFSA (2013) but their repeatability is still a gap of knowledge. Therefore, the aim of the present study was to assess the repeatability between observers of the most valid and feasible indicators of consciousness after waterbath stunning in poultry. This study proposes a refined list of indicators that could be used to assess the state of consciousness of turkeys in commercial slaughterhouses and reports on the efficacy of stunning of different key electrical parameters. The prevalence and inter-observer repeatability of the four most valid and feasible indicators of consciousness after waterbath stunning in turkeys were evaluated before bleeding (i.e., tonic convulsion, breathing, spontaneous blinking and vocalization) and during bleeding (i.e., fluttering, breathing, spontaneous swallowing and head shaking). Furthermore, correlations between them were calculated to further understand the association between such indicators. This study compared the assessments of four observers on 7877 turkeys from 28 flocks slaughtered in eight different abattoirs. Repeatability between observers was assessed by combining the crude percentage of agreement and the Fleiss' kappa. Before bleeding, tonic seizure was observed to be not reliable under commercial conditions and spontaneous blinking and vocalization had poor repeatability. During bleeding, spontaneous swallowing was not observed and head shaking had poor repeatability. Hence, the most relevant indicators of consciousness before bleeding is breathing while during bleeding is breathing and wing flapping. Moreover, the stunning efficiency of the key electrical parameters used in the different slaughterhouses was assessed. Therefore, a refined list of indicators of the state of consciousness after waterbath stunning is proposed to be used in commercial turkey slaughterhouses to ensure consistency of controls. On the other hand, the range of the prevalence of turkeys with indicators of consciousness within a batch found before bleeding [0-16%] and after bleeding [0-18%] highlights the importance of controls.