Effect of physical and inhaled euthanasia methods on hormonal measures of stress in pigs

Abstract

Objective: To determine the effect of physical and inhaled euthanasia methods on mean plasma levels of three hormonal stress indicators in young pigs. Materials and methods: Plasma concentrations of cortisol, norepinephrine, and lactate were determined immediately before and after two-step electrocution (n = 39; 7.1 ± 0.5 kg), captive bolt (n = 61; 12.3 ± 1.9 kg), 70% N2/30% CO2 at a displacement rate equivalent to 20% of the chamber volume per minute (n = 16; 2.3 ± 0.3 kg), and 100% CO2 at 10% (n = 4; 1.9 ± 0.2 kg) and 20% (n = 12; 1.9 ± 0.1 kg) chamber volume displacement rate per minute. Results: Mean cortisol concentrations did not differ following captive bolt, electrocution, and 70% N2/30% CO2 or 100% CO2 at 20% of the chamber volume per minute (P > .05). The decrease in cortisol concentrations with 100% CO2 at 10% of the chamber volume per minute was different (P < .05) than the increase observed with 100% CO2 at 20% of the chamber volume per minute and different (P < .05) than the increase observed with captive bolt; however, differences were small. All methods increased mean lactate and norepinephrine concentrations post euthanasia, with no observed differences between methods. Times to loss of consciousness and loss of heartbeat were shorter with CO2 than with 70% N2/30% CO2 (P < .05). Implications: Gradual displacement administration of CO2 and 70% N2/30% CO2 produce similar plasma concentrations of stress indicators as physical euthanasia methods in young pigs.