Developing best management practices for on-farm euthanasia of young pigs using carbon dioxide gas
The use of carbon dioxide has the potential to be a practical method of on-farm euthanasia for young pigs in farrowing as an alternative to blunt force trauma, where the pigs’ small size makes the use of a captive bolt dangerous and impractical. For carbon dioxide (CO2) to become a practical on-farm alternative to blunt force trauma it is necessary to develop best management practices for the use of carbon dioxide on commercial swine farms taking into consideration animal welfare and worker safety. The objective of this study was to develop best management practices for euthanasia of young pigs using a carbon dioxide. In experiment 1, pigs of six different ages (1, 2, 3, 4, 5, and 6 weeks of age) were euthanized in a chamber measuring 76.6 cm X 42.6 cm X 50.0 cm and CO2 was gradually released at a flow rate of 20% per min. To assess the well-being of pigs during CO2 euthanasia, physiological and behavioral measures of stress were recorded. Heart rate and brain activity were used to assess time of death. Age differences in the behavioral response to CO2 were observed, but these age differences were only small and deemed not significant enough to develop different euthanasia methodologies for pigs of different ages. The same equipment used in experiment 1 was taken onto a commercial swine farm and the same procedure that was validated in experiment 1 was used to euthanize young pigs of various ages. It quickly became apparent that it was not practical to use the above method on a commercial farm as pigs took approximately 7 min to die. Therefore, in experiment 2 the physiological and behavioral responses of young pigs to CO2 euthanasia using the gradual and prefill methods were compared. The behavioral response to CO2 euthanasia differed between methods of gas administration. Furthermore, the time to death was shorter in pigs euthanized using the prefill compared with the gradual fill method as measured by brain activity (Gradual: 461.6 s; Prefill: 248.2 s) and heart rate (Gradual: 464.7 ± 22.9 s; Prefill: 313.4 ± 56.1 s). Based on these results, the prefill method of euthanasia appears more humane than the gradual fill method, therefore best management practices were written based on the prefill method rather than the gradual fill method.
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