Agonic Aspiration of Blood: Not Useful as an Animal-Based Indicator of Electrical Stunning Ineffectiveness in Pigs (Sus scrofa domesticus)

Simple Summary Agonic aspiration of blood should be seen as a critical welfare problem in the slaughter of pigs, as it reflects a moment of pain, distress, and fear for the animal during its time of death. Our survey focused on assessing whether lesions of agonic blood aspiration could be used as a valuable indicator to guide the official veterinarian to immediately apply the necessary measures to ensure good practices of animal welfare at slaughter. Ineffective electrical stunning of pigs has been associated with the incidence of lung lesions suggestive of agonic blood aspiration at postmortem inspection. However, for the first time, the findings from this study indicate that aspiration of blood may be related to factors other than agonic status during slaughter process. One of them being that horizontal bleeding may favour slaughter technopathies. This process should not be neglected, as it may result in lesions resembling those resulting from the agonic lung aspiration of blood-which is not related to an agonic status. Agonic aspiration of blood (AAB) may result from an inadequate exsanguination with accidental trachea severing, that can be favoured by ineffective stunning of pigs (Sus scrofa domesticus). This study aimed to evaluate AAB as an animal-based indicator of electrical stunning ineffectiveness, which could be used by official veterinarians during the post-mortem inspection of pigs. Information on 3584 finishing pigs was collected at a Portuguese abattoir that performs head-to-body electrical stunning with horizontal bleeding. Of them, 15.5% of the pigs presented signs of ineffective stunning. AAB lung lesions were found in 27.8% of lungs. Despite what was predicted, a strong correlation was found between well stunned animals and the presence of blood lesions in lungs (p = 0.006). Statistical significances were found between pigs' lateral recumbency at the conveyor and the presence of blood affecting one lung. Under the conditions of this study, the authors cannot point to AAB lung lesions as an animal-based indicator of electrical stunning ineffectiveness. Further studies should be conducted to establish a better understanding of the causes of aspiration of blood, in particular how horizontal bleeding may affect the occurrence of similar lesions.