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Swine Respiratory Disease Minimally Affects Responses of Nursery Pigs to Gas Euthanasia

25 June 2014

New research from Iowa State University reveals that standard operating procedures for gas euthanasia do not require adjustment for nursery pigs with respiratory disease. For carbon dioxide, the minimum exposure to 70 per cent carbon dioxide concentration respiratory arrest was 10 minutes. The effective time and concentration for argon remain unknown.

In Journal of Swine Health and Production, Larry J. Sadler and colleagues at Iowa State Univeristy report their experiments to assess the effects of swine respiratory disease (SRD) on nursery pig responses during gas euthanasia and to compare responses to carbon dioxide (CO2) and argon (Ar) gas euthanasia in terms of efficacy and welfare.

A total of 54 pigs identified for euthanasia were classified as having SRD or euthanized for other reasons (OT). These pigs were distributed among three treatments: pre-fill CO2 (P-CO2), gradual fill CO2 (G-CO2) and pre-fill Ar (P-Ar).

Behavioural and physiological indicators of efficacy and welfare were assessed directly and from video. Modified atmosphere carbon dioxide and oxygen concentrations were collected throughout the process.

Respiratory disease status did not affect behavioural or physiological responses associated with efficacy or welfare with P-CO2 or G-CO2. Conversely, SRD pigs lost consciousness faster than OT pigs with P-Ar (P<0.05) and duration of open-mouth breathing was shorter (P<0.05), but duration of ataxia tended to be longer (P<0.10).

Regardless of disease status, P-CO2 was associated with superior animal welfare, with shorter latency to loss of consciousness than P-Ar, and shorter duration of ataxia and duration and intensity of righting responses.

Standard operating procedures for gas euthanasia utilising carbon dioxide or argon do not require adjustment for nursery pigs with respiratory disease, according to Sadler and co-authors. Minimum exposure of 10 minutes at more than 70 per cent carbon dioxide concentration is required reliably to produce respiratory arrest in nursery pigs.

The researchers added that argon is not recommended as a euthanising agent for nursery pigs and the duration of exposure to argon required to produce respiratory arrest reliably remains unknown.


Sadler, L.J., L.A. Karriker, A.K. Johnson, K.J. Schwartz, T.M. Widowski, C. Wang and S.T. Millman. 2014. Swine respiratory disease minimally affects responses of nursery pigs to gas euthanasia. J. Swine Health Prod. 22(3):125–133.

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June 2014

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