The study seeks to evaluate the effectiveness of euthanasia in mink (Neovison vison). The gases studied were filtered exhaust CO, and cylinder CO and CO2. The experimental setups were as follows: (1) individual killing of mink in a small killing box (35 × 30 × 60 cm; H × W × L); (2) individual killing of mink in a small killing box, kept inside a killer (12.5 × 12.5 × 55 cm; H × W × L); (3) group killing of mink in a large killing box (75 × 75 × 150 cm; H × W × L); and (4) group killing of mink in a large killing box (70 × 70 × 125 cm; H × W × L). The results showed that filtered exhaust CO concentrations of 1.2-3% were too low. Concentrations of 4-6% were effective. With cylinder CO of 4% the killing time was the same as that with engine CO at 4%. A cylinder CO2 concentration of ≥ 80% was effective. The shortest time interval after the end of all movements and respiration was with cylinder CO2. No difference was found between cylinder and filtered exhaust CO. The time the animals were alive did not significantly differ between the groups (P>0.05). The first animal collapsed soonest among those inhaling CO2 (CO2 vs cylinder CO; P=0.0045; and CO2 vs filtered exhaust CO; P=0.0009). No difference was found between cylinder CO and filtered exhaust CO (P=0.4654). There was also a significant difference in the time it took for the last animal to collapse. Here again the CO2 animals collapsed the soonest (CO2 vs cylinder CO, P=0.0062; CO2 vs exhaust CO, P=0.0012). No difference was found between cylinder and filtered exhaust CO (P=0.5660). It is concluded that concentrations of CO ≥4% and of CO2 ≥80% in the euthanasia box are sufficient to kill effectively.
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