Abstract
Situations may arise where authorities need to depopulate large quantities of pigs in a short time. This must be done in an animal welfare-responsible manner. This paper describes in detail a technical mobile container system for CO(2) depopulation of pigs. The system consists of simple and easily accessible materials and can be replicated and scaled for multiple container systems for CO(2) depopulation. The container system was tested at 4 depopulation events where the pigs' behavior was filmed (1 event) and the duration of the various procedures was recorded. The results showed that the system's capacity met AVMA's recommendations for a CO(2) supply rate of 10% to 30% of the chamber volume per min. On average, the containers were supplied with CO(2) for 7 min, and it was possible to maintain a CO(2) concentration of 80% for at least 10 min after stopping the CO(2) admission. By maintaining the tarpaulin on the container during transport, this "extending effect period" can be utilized for additional CO(2) exposure and acts as an extra safeguard for successful depopulation. Target CO(2) concentration of 80% occurred after a mean of 7 min. Pig escape attempts were first observed 2 min:26 s after the start of CO(2) exposure. Presumably due to the stocking density (a mean of 0.52 m(2) per pig), no loss of posture (indicating loss of consciousness) could be observed. On the other hand, the last escape attempts were observed after 3 min:04 s, and the last atactic movements after 3 min:13 s. It is therefore reasonable to assume that all pigs have lost consciousness around that time. No pigs survived the procedure, and the described CO(2) depopulation system therefore lived up to expectations. We recommend that users are given the opportunity to practice thoroughly before an authentic emergency.