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Journal of Animal Science Abstract - Animal Production

Effects of flow rate and gas mixture on the welfare of weaned and neonate pigs during gas euthanasia1


This article in JAS

  1. Vol. 92 No. 2, p. 793-805
    Received: Apr 16, 2013
    Accepted: Nov 22, 2013
    Published: November 24, 2014

    2 Corresponding author(s):

  1. L. J. Sadler 23,
  2. C. D. Hagen,
  3. C. Wang‡§,
  4. T. M. Widowski#,
  5. A. K. Johnson and
  6. S. T. Millman*‡
  1. Department of Biomedical Sciences, Iowa State University, Ames 50011
    Value-Added Science and Technologies (VAST), Mason City, IA 50401
    Department of Veterinary Diagnostic and Production Animal Medicine, Iowa State University, Ames 50011
    Department of Statistics, Iowa State University, Ames 50011
    Department of Animal and Poultry Science, University of Guelph, Guelph, ON N1G 2W1, Canada
    Department of Animal Science, Iowa State University, Ames 50011


The objectives of this study were to assess efficacy and welfare implications of gas euthanasia when applied to weaned and neonate pigs. Parameters associated with welfare, which were measured before loss of consciousness, included open-mouth breathing, ataxia, righting response, and escape attempts. Two age groups (weaned and neonate) were assessed in 9 gas treatments arranged in a 2 × 4 factorial design, with 2 gas types (CO2 = 100% CO2 and 50:50 = 50:50 CO2:argon) and 4 flow rates (box volume exchange/min: slow = 20%; medium = 35%; fast = 50%; prefill = prefilled followed by 20%) and a control treatment in which ambient air was passed through the box. Pig pairs (10/treatment) were placed in a modified Euthanex AgPro system (Euthanex Corp., Palmer, PA). Behavioral and physiological responses were observed directly and from video recordings for latency, duration, prevalence (percent of pigs affected), and frequency (number of occurrences/pig). Data were analyzed as linear mixed models or with a Cox proportional hazard model as appropriate. Piglet pair was the experimental unit. For the weaned pig, welfare was superior with CO2 relative to 50:50 within 1 or more flow rates on the basis of reduced duration of open-mouth breathing, duration of ataxia, frequency of escape attempts, and duration and frequency of righting response (P < 0.05). No measured parameters indicated superior welfare with the use of 50:50, whereas latencies to loss of posture and last movement favored CO2 (P < 0.05). Faster flow rates were associated with reduced (P < 0.05) duration or frequency of open-mouth breathing, ataxia, and righting response, as well as superior (P < 0.05) indicators of efficacy, including latencies to loss of posture, gasping, and last movement, relative to slower flow rates. Weaned pigs were more likely to defecate (P < 0.01), display nasal discharge (P < 0.05), and display longer (P < 0.001) latencies to loss of posture and last movement than neonates. Duration of ataxia was the only parameter for which neonates were superior (P < 0.01) to weaned pigs during euthanasia. As such, a 50:50 CO2:argon gas mixture and slower flow rates should be avoided when euthanizing weaned or neonate pigs with gas methods. Neonate pigs succumb to the effects of gas euthanasia quicker than weaned pigs and display fewer signs of distress.

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