When and what determines the death of an animal? A study investigating the heart activity during slaughter of farm animals

Sammanfattning: Slaughter of animals should consist of two steps in order to be considered humane. The first step of the slaughter process is stunning, with the purpose of inducing unconsciousness and insensibility in the animal. The second step is exsanguination, which causes bleeding and eventually death. What death really means in these situations has been discussed intensively, but still no agreed definition has been accepted. Nonetheless, it is conceded that animals are declared dead when consciousness is irreversibly lost, and absence of respiration and blood circulation are observed. The Swedish Animal Welfare Act states that during slaughter, no further measures may be taken on the animal until its death has occurred. One question that arises is in respond to this is: Is an animal really dead, even though the heart beats, when the remainder of the slaughter process commences after stunning and exsanguination? The aim of this thesis was to investigate heart activity after stunning and exsanguination of cattle and fattening pigs at conventional commercial slaughter plants in Sweden in order to determine the exact time of cardiac arrest. In total, 108 cattle and 157 pigs from three different slaughter plants were observed using two different stethoscopes. A significant difference was found between the stethoscopes for both cattle and pigs (p ≤0.0001). Furthermore, significant differences were found between the two slaughter plants where data was collected on pigs (p ≤0.0001), but not between the slaughter plants where data was measured on cattle (p=0.24). The time from start of exsanguination to cardiac arrest was on average 5 minutes and 45 seconds for cattle and 2 minutes and 58 seconds for pigs. In conclusion, this study suggests that the definition of death in animal welfare contexts should be based both upon loss of brain and cardiac function. In future studies, this can be used to evaluate the possible implications this would have for the slaughter process and also the animal welfare.