Effectiveness of electrical stunning and bleeding in finishing pigs: a case study from procedures to practice at two modern Colombian abattoirs

The utilisation of electrical equipment for the purpose of stunning animals prior to slaughter is a common practice in pig abattoirs across the world. The aim of this study was to evaluate the efficacy of two-electrode electrical stunning on behavioural markers of unconsciousness in two commercial systems of physical restraint and exsanguination. A total of 959 Landrace X Large White commercial crossbred pigs, with an average live weight of 107.1 ± 10.7 kg, were assessed in two modern Colombian abattoirs. The pigs were desensitised using electrical stunning at two points, with different equipment and procedures employed at each site. The evaluations were conducted at three distinct stages: immobilisation, stunning and bleeding. The data were subjected to bivariate analysis and univariate and multivariate binary logistic regression across three stages: pre-stunning, stunning, and bleeding. The results demonstrated a markedly elevated level of behavioural reactivity during the herding process (p < 0.05) and at the stunning stage (p < 0.001) in both abattoirs. The percentage of pigs exhibiting at least one post-stunning reflex was higher in Abattoir A, while Abattoir B demonstrated a higher percentage of pigs with at least one post-bleeding reflex (p < 0.001). Moreover, notable correlations were observed between behavioural reactivity or reflexes and specific animal characteristics or logistical conditions (p < 0.05). Furthermore, distinct animal profiles were identified based on behavioural and consciousness indicators observed during stunning and bleeding procedures, contingent on the abattoir in question. The findings illustrate that a considerable number of animal welfare concerns do not manifest universally across all abattoirs, despite the utilisation of analogous stunning techniques. Consequently, it is imperative to further refine the risk analysis approach associated with specific scenarios, in addition to cross-cutting ones across multiple scenarios.