Euthanasia of meat rabbits with carbon dioxide: Behavioral and physiologic responses to gas chamber gradual- and fast-fill rates.

The use of CO2 inhalation with different gas chamber fill rates has not been evaluated for euthanasia in commercial meat rabbits. Our objectives were to evaluate the behavioral and physiologic responses of rabbits (pre-weaned to adult) when exposed to gradual- and fast-fill rates of CO2, and to determine the time to onset of insensibility and death. Cull rabbits (n = 81) were randomly assigned to either a gradual-fill chamber displacement rate of 28% volume change/min (n = 42) or a fast-fill chamber displacement rate of 58% volume change/min (n = 39). The fast-fill rate resulted in a more rapid loss of sensibility at a lower CO2 chamber concentration and in a faster death than for gradual-fill. There were minimal differences in behavioral responses between fill rates with no clear signs of distress. These findings indicate that CO2 at the studied displacement rates is suitable for commercial meat rabbit euthanasia.