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Effect of Physical and Inhaled Euthanasia Methods on Hormonal Measures of Stress in Pigs

19 November 2013

In a US study, similar plasma concentrations of stress indicators were observed in young pigs with physical euthanasia methods and the gradual displacement administration of carbon dioxide or a mix of 70 per cent nitrogen and 30 per cent carbon dioxide.

Researchers at Mississippi State University, North Carolina State University and USDA APHIS Veterinary Services have investigated the effect of physical and inhaled euthanasia methods on mean plasma levels of three hormonal stress indicators in young pigs.

In Journal of Swine Health and Production, first-named author, Robert E. Meyer and his co-authors explain that they determined plasma concentrations of cortisol, norepinephrine, and lactate immediately before and after two-step electrocution (n=39; 7.1±0.5kg), captive bolt (n=61; 12.3±1.9 kg), 70 per cent nitrogen/30 per cent carbon dioxide (70N2/30CO2) at a displacement rate equivalent to 20 per cent of the chamber volume per minute (n=16; 2.3±0.3 kg) and 100 per cent carbon dioxide at 10 per cent (n=4; 1.9±0.2 kg; 10CO2) and 20 per cent (n=12; 1.9±0.1kg; 20CO2) chamber volume displacement rate per minute.

Mean cortisol concentrations did not differ following captive bolt, electrocution, and 70N2/30CO2 or 20CO2 of the chamber volume per minute (P>0.05). The decrease in cortisol concentrations with 10CO2 was different (P<0.05) from the increase with 20CO2 (P<0.05) and different from the increase observed with the 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 carbon dioxide than with 70N2/30CO2 (P< 0.05).

Meyer and co-authors concluded that gradual displacement administration of carbon dioxide and 70N2/30CO2 produce similar plasma concentrations of stress indicators as physical euthanasia methods in young pigs.


Meyer R.E., J.T. Whitley, W.E.M. Morrow, L.F. Stikeleather, C.L. Baird, J.M. Rice, B.V. Halbert, D.K. Styles and C.S. Whisnant. 2013. Effect of physical and inhaled euthanasia methods on hormonal measures of stress in pigs. J Swine Health Prod. 21(5):261–269.

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November 2013

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