Comparison of stunning methods on consciousness in pigs during slaughter

Abstract

The slaughter of livestock is inevitably required to obtain meat products from livestock. Since slaughter means pain and death for animals, reducing the pain and distress of animals during slaughter is very important from a perspective of animal welfare based on the principle of respect for life. Generally, two stunning methods, CO2 stunning and electrical stunning, are used for slaughter. When the carotid arteries of the lungs are cut off for bleeding, the bronchial tubes are also severed. To determine the degree of blood inflow into the lungs through the severed bronchial tubes, the prevalence rates of pulmonary diseases and pulmonary congestion in slaughtered pigs were analyzed. In this study, the prevalence of pneumonia was 24.9% in Slaughterhouse A using the gas method, but it was decreased by about 10% to 15.7% and 12.6%, respectively, in Slaughterhouses B and C using the electric method. On the other hand, the prevalence of pulmonary congestion in Slaughterhouses A, B, and C was 4.24%, 14.10% and 16.40%, respectively. In other words, the prevalence of pulmonary congestion was higher by about 10% in the groups of pigs slaughtered by the electric method (Slaughterhouses B and C) than in the group of pigs slaughtered by the gas method (Slaughterhouse A). These results indicate that blood inflow into the pulmonary alveoli led to a diagnosis of pulmonary congestion instead of pneumonia in some pigs with pneumonia. In short, it was found that about 10% of pigs stunned by the electric method were not in a state of complete unconsciousness but in a partially conscious state during slaughter. It is suggested that slaughterhouses should be equipped with gas stunning equipment instead of applying the electric method due to lower costs.