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

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.

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

“…Head shaking could be placed in a second level of attention while spontaneous swallowing could be not even considered. When comparing these results with those obtained previously in broiler chickens [17], the same indictors are recommended before bleeding in both poultry species. However, spontaneous swallowing was observed in very few broiler chickens but never in turkeys while head shaking was considered as a relevant ABI in broiler chickens, but it is not in turkeys during bleeding.…”

“…SHs were from two turkey producer countries in Europe and despite of not being selected randomly, still represent a wide variety of SH designs, key electrical parameters applied, line speeds and turkey's body weight. Regarding the observers, all of them were well trained, conducted a similar study in broiler chickens with a κ value of 0.77 [17] and agreed on the definition of the ABIs before the assessments. The number of observers was kept to the maximum number possible with the intention of causing minimum interference to the operators and to each other.…”

“…The selected ABIs before bleeding were tonic seizure, breathing, spontaneous blinking and vocalizations, while the selected ones during bleeding were wing flapping, breathing, spontaneous swallowing and head shaking. The description of the outcomes of consciousness and unconsciousness of these ABIs are those reported by Contreras-Jodar et al [17] and are summarized in Table 3.…”

“…Slaughter line speeds ranged from 300 to 3000 turkeys/h. The assessment of turkeys' state of consciousness was carried out by four trained observers that conducted a similar study in broiler chickens (using the same ABIs for the state of consciousness) with an overall κ value of 0.77 [17]. Each observer was named as letter (A to D).…”

“…Thus, it is of utmost importance to gain insight into which are the most relevant ABIs for monitoring the state of consciousness in poultry and select them, ensuring consistency of controls. Recently, a refined list of ABIs for broiler chickens was proposed [17] but no refined list exists for any other poultry species.…”