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

Abstract

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 (CO 2 = 100% CO 2 and 50:50 = 50:50 CO 2 :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 CO 2 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 CO 2 (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 CO 2 :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. This is a manuscript of an article that is not peer-reviewed from Journal of Animal Science 92 (2014): 793, doi:10.2527/jas.2013-6598. ABSTRACT: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 prior to 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 (CO 2 = 100% CO 2 or 50:50 = 50:50 CO 2 :argon) and 4 flow rates (box volume exchange/min: slow = 20%; medium = 35%; fast...

Effectiveness of a nonpenetrating captive bolt for euthanasia of 3 kg to 9 kg pigs1

“…In terms of the visual esthetics of technique, the convulsive stage, arguably the most disturbing period to an unfamiliar audience, was actually shorter for weaned pigs than the durations reported for neonates (Casey-Trott et al, 2013). Conversely, Sadler et al (2014) observed that neonates succumbed faster than weaned pigs when using inhalant euthanasia techniques with carbon dioxide and argon gases. This contrasting result may be related to the differences in the mode of action between physical and gaseous euthanasia techniques, with physical methods causing direct destruction of neuronal tissues and gaseous methods causing hypoxic conditions in the brain leading to tissue death (AVMA, 2013).…”

“…These grand mal convulsive movements are involuntary neuromuscular responses indicative of epileptiform brain activity following severe concussion (Shaw, 2002) and during electrical stunning in pigs (McKinstry and Anil, 2004). Varying degrees of these convulsive movements have been reported following application of all available euthanasia techniques for pigs including BFT and NPCB (Chevillon et al, 2004;Widowski et al, 2008;Woods, 2012) and CO 2 (Raj and Gregory, 1996;Sutherland, 2010;Sadler et al, 2014). The convulsive period was similar to the 1 to 1.5 min typically seen with BFT (Chevillon et al, 2004;Widowski et al, 2008) and shorter than other NPCB devices falling within the range or 1 to 4 min reported by Woods (2012).…”

Evaluation of Different Gases and Gas Combinations for On-Farm Euthanasia of Pre-Weaned Pigs

“…Several gases are currently used to euthanise, stun or kill animals, including CO 2 and the inert gases, argon (Ar) and nitrogen [ 10 , 11 , 12 , 13 ]. Gaseous methods are routinely used for laboratory rodents, with CO 2 being the most commonly used agent because it is heavier than air and thus containable, cheap to obtain and relatively safe for human operators [ 14 , 15 , 16 , 17 ].…”

The use of carbon dioxide (CO2) as an alternative euthanasia method for goat kids

“…Elimination behavior in kids was low across all days, and did not increase or decrease consistently. Escape attempts are generally observed when an animal is in an environment that is perceived as threatening, and escape attempts are exhibited in pigs and rodents during gas exposure (Niel and Weary, 2006, Llonch et al, 2012, Chojnacki et al, 2014, Sadler et al, 2014b, Barnard et al, 2015. The lack of escape attempts during gas treatments may be an indicator of a lack of fear in response to CO2, but it may also be associated with the ataxia that accompanies CO2 exposure.…”

“…CO2/minute box volume replacement rate (Gerritzen et al, 2004, Sadler et al, 2014a. While this induction time is relatively fast, there is still the potential for distress and pain during the animals' conscious period.…”