View Full Table | Close Full ViewTable 1.

Temperature and relative humidity during euthanasia of weaned pigs

 
Temperature, °C
Relative humidity, %
Treatments1 Starting2 Change3 Starting2 Change3
AMB 26.3 –0.3 62.4 2.0
CO2
    Prefill 26.4 –0.1 62.3 2.1
    Fast 26.3 –0.3 73.6 5.4
    Medium 25.8 –0.2 68.5 4.7
    Slow 26.1 –0.0 64.4 3.9
50:50
    Prefill 26.3 –0.4 70.6 2.5
    Fast 26.2 –0.2 72.3 3.7
    Medium 26.2 –0.2 71.6 4.5
    Slow 26.5 –0.1 63.4 3.8
SEM 0.8 0.1 5.0 2.8
1AMB = pigs euthanized by blunt-force trauma after being placed in the box for 10 min; CO2 = euthanized with 100% CO2; 50:50 = euthanized with a 50:50 mixture of CO2 and argon; Prefill = pigs placed in box prefilled with the appropriate gas followed by a gas flow rate of 20% box volume/min; Fast = gas flow rate of 50% box volume/min; Medium = gas flow rate of 35% box volume/min; and Slow = gas flow rate of 20% box volume/min.
2Recorded on pig placement in euthanizing box.
3Change that occurred in the box from the time of placement until pig removal from the box.



View Full Table | Close Full ViewTable 2.

Temperature and relative humidity during euthanasia of neonate pigs

 
Temperature, °C
Relative humidity, %
Treatments1 Starting2 Change3 Starting2 Change3
AMB 23.1 0.0 79.2 9.2
CO2
    Prefill 22.6 –0.0 55.4 1.5
    Fast 23.6 –0.0 46.0 2.6
    Medium 23.5 –0.1 57.4 4.6
    Slow 23.3 –0.0 61.2 4.3
50:50
    Prefill 22.7 –0.4 55.4 2.9
    Fast 22.8 –0.2 52.9 3.7
    Medium 23.3 –0.1 59.4 4.5
    Slow
SEM 0.8 0.1 3.9 2.8
1AMB = pigs euthanized by blunt-force trauma after being placed in the box for 10 min; CO2 = euthanized with 100% CO2; 50:50 = euthanized with a 50:50 mixture of CO2 and argon; Prefill = pigs placed in box prefilled with the appropriate gas followed by a gas flow rate of 20% box volume/min; Fast = gas flow rate of 50% box volume/min; Medium = gas flow rate of 35% box volume/min; and Slow = gas flow rate of 20% box volume/min.
2Recorded on pig placement in euthanizing box.
3Change that occurred in the box from the time of placement until pig removal from the box.



View Full Table | Close Full ViewTable 3.

Ethogram developed for investigating latency, duration, prevalence, and frequency of behavioral indicators of distress and insensibility during euthanasia

 
Postures Definition Direct Video1
    Standing/locomotion2 Maintaining an upright and stationary body position by supporting the BW on the feet with the legs extended or movement derived from the repulsive force from the action of the legs. L
    Sitting2 A body position in which the posterior of the body trunk is in contact with the ground, sides of the box, or the other pig, and supports most of the BW. L
    Lying2 Maintenance of a recumbent position. L
    Ataxic movement3 Pig is moving in a seemingly uncoordinated fashion; lack of muscle coordination during voluntary movement. L
    Righting response Pig is making attempt to maintain either a standing or lying sternal posture but is not successful in maintaining the position (different from muscular excitation in that these are slower and seemingly coordinated movements); The event was defined as each time effort was made and the muscle relaxed. L
    Muscular excitation4, 5 Repeated muscular movement of the whole body, including head movements upward; seemingly uncoordinated (categorizing posture is not possible due to rapid and frequent movements); severe excitation appears as major clonic convulsive seizures. L
    Out of view Pig could not be seen clearly enough to identify the behavior or position, or pig was removed from box. L
    Other posture Pig’s posture was not defined by previous definitions. L
Behaviors
    Oral nasal facial (ONF)6 Rubbing, licking, biting, touching the mouth, snout or face to 1 of 2 modifiers– other pig or item (walls, flooring, or cage). L
    Licking and chewing6 Pig is going through motions of licking and chewing, similar to ONF but not interacting with an object or the other conspecific. L7 L
    Open-mouth breathing 7,8 Pig’s mouth is open, taking in quick breaths (panting), with distinct thoracic movements; upper and lower jaw being held open with the top lip pulled back, exposing gums or teeth and panting (pronounced inhalation and exhalation observed at the flanks). L7 L
    Gasping4,7 Rhythmic breaths characterized by very prominent and deep thoracic movements, with long latency between (may involve stretching of the neck); often occurs right before or after loss of posture. L7 L
    Out of view Pig could not be seen clearly enough to identify the behavior or position, or pig was removed from box. L
    Other behavior Pig’s behavior was not defined by previous definitions.
Events
    Salivation Fluid discharge coming from mouth; type of discharge (may be clear and fluid, viscous, or blood) was noted. L
    Nasal discharge Discharge from the nasal cavity; type of discharge (may be clear and fluid, viscous, or blood) was noted. L
    Eye orbit discharge Discharge from the ocular orbit; type of discharge (may be clear and fluid, viscous, or blood) was noted.
    Defecation2 Elimination of feces from the body. L
    Urination2 Discharge of urine from the body. L
    Vomiting2 Ejection of gastrointestinal contents through the mouth. L
    Escape attempt, bout7,9 Pig is raising their forelegs on the side of the wall of the box or pushing quickly and forcefully with their head or nose on the lid of the box; forceful coordinated movement against the exterior of the box; occurrences within a 10-s period will be recorded as a single bout. L
    Loss of posture7,9 Pig is slumped sown, making no attempt to right itself; may follow a period of attempts to maintain posture (considered first indicator of loss of consciousness). L L
    Last movement No movement, of any kind is observed from the pig. L
1For video, each pig was scored for 1 of 8 mutually exclusive postures and concurrently for 1 of 6 mutually exclusive behaviors, along with event behaviors if they occurred.
2Adapated from Hurnik et al. (1985).
3Adapted from Blood et al. (2007).
4Adapted from Dodman (1977).
5Adapated from Rodríguez et al. (2008).
6Adapated from Meiszberg et al. (2009).
7All direct observations were scored as events.
8Adapted from Velarde et al. (2007).
9Adapted from Johnson et al. (2010).
10Adapted from Raj and Gregory (1996).



View Full Table | Close Full ViewTable 4.

Effect of euthanasia method on the mean duration ± SE (seconds) of weaned and neonate pigs displaying behavioral indicators of distress

 
100% CO2 gas3
50:50 CO2 and argon gas mixture (50:50)3
Distress measures,1 s AMB2 Prefill Fast Medium Slow Prefill Fast Medium Slow
Weaned pigs
    Standing and locomotion 241 ± 18a 15 ± 30b 58 ± 25b 61 ± 15b 79 ± 15b 23 ± 31b 76 ± 26b 86 ± 15b 115 ± 15b
    Oral nasal, all 139.3 ± 5.0a 0.0 ± 0.0c 3.6 ± 1.3b 3.6 ± 1.0b 5.2 ± 1.3b 0.0 ± 0.0c 5.1 ± 1.3b 4.1 ± 1.5b 11.1 ± 3.6b
    Licking and chewing 27.3 ± 5.0a 1.4 ± 0.4b 20.7 ± 2.5a 11.0 ± 1.7a 18.4 ± 2.7a 4.0 ± 1.2b 20.2 ± 2.9a 13.1 ± 2.9a 33.6 ± 7.5a
    Open-mouth breathing 0f 20 ± 2e 26 ± 2d 34 ± 2c 45 ± 3b 35 ± 2c 46 ± 3b 64 ± 5a 72 ± 5a
    Ataxia 0g 14 ± 1f 19 ± 2e 21 ± 2d 39 ± 4c 35 ± 5c 40 ± 5c 46 ± 5b 52 ± 5a
    Righting response 0d 1.2 ± 0.7c 0.3 ± 0.8c 3.7 ± 1.7b 4.2 ± 1.3b 11.2 ± 2.6a 8.7 ± 2.2a,b 4.7 ± 2.2b 13.7 ± 3.2a
    Clonic movement 0d 50 ± 7c 55 ± 5b,c 61 ± 5b,c 84 ± 6a 79 ± 6a,b 65 ± 5b,c 70 ± 5b,c 93 ± 6a
    Gasping 0e 224 ± 12c 174 ± 11d 198 ± 12c,d 346 ± 12b 371 ± 13b 280 ± 12c 344 ± 12b 478 ± 12a
Neonate pigs
    Standing and locomotion 309 ± 18a 15 ± 30b 36 ± 15b 37 ± 15b 55 ± 15b 8 ± 31b 48 ± 26b 58 ± 15b
    Oral nasal, all 53.3 ± 21.6a 0.0 ± 0.0c 1.4 ± 1.3b 1.0 ± 1.0b 0.7 ± 1.3b 0.0 ± 0.0c 2.0 ± 1.3b 3.4 ± 1.5b
    Licking and chewing 6.9 ± 4.8 0.0 ± 0.0 5.3 ± 2.5 4.0 ± 1.7 5.2 ± 2.7 1.3 ± 2.0 2.9 ± 3.0 2.0 ± 3.0
    Open-mouth breathing 0e 12 ± 2d 23 ± 2c 24 ± 2c 39 ± 3b 14 ± 2d 34 ± 3b 49 ± 5a
    Ataxia 0e 14 ± 1d 27 ± 2c 26 ± 2c 43 ± 4b 24 ± 5c 47 ± 5b 66 ± 5a
    Righting response 0b 2.3 ± 0.7a 3.6 ± 0.8a 4.9 ± 1.7a 1.9 ± 1.3a 3.7 ± 2.6a 4.6 ± 2.2a 8.0 ± 2.2a
    Clonic movement 0d 41 ± 5b,c 37 ± 5b,c 27 ± 5c 33 ± 6c 66 ± 6a 59 ± 5a 58 ± 6a,b
    Gasping 0f 210 ± 12e 225 ± 11e 247 ± 12d,e 348 ± 12b 374 ± 12a 308 ± 13c 346 ± 12b
a– gWithin a row, least squares means (±SE) lacking a common superscript letter differ (P < 0.05).
1Refer to Table 3 for a description of each behavior.
2AMB = pigs euthanized by blunt-force trauma after being placed in the box for 10 min.
3Prefill = pigs placed in box prefilled with the appropriate gas followed by a gas flow of 20% box volume/min; Fast = gas flow rate of 50% box volume/min; Medium = gas flow rate of 35% box volume/min; and Slow = gas flow rate of 20% box volume/min.



View Full Table | Close Full ViewTable 5.

Effect of euthanasia method on the frequency (%) of weaned and neonate pigs displaying behavior indicators of sensation and distress

 
Distress measures,1 % AMB2 100% CO2 gas3
50:50 CO2 and argon gas mixture (50:50)3
Prefill Fast Medium Slow Prefill Fast Medium Slow
Weaned pigs
    Standing and locomotion 100 100 100 100 100 100 100 100 100
    Oral nasal, all 90 0 40 45 65 0 55 40 55
    Licking and chewing 40 5 70 60 45 10 50 40 44
    Escape attempts 0b 0b 0b 0b 0b 15a 10a 15a 15a
    Defecation 35 25 45 45 50 50 60 50 45
    Urination 10 15 20 10 10 30 35 35 5
    Salivation 15 5 5 0 15 10 10 30 50
    Nasal discharge 10 0 10 20 25 15 5 20 30
    Open-mouth breathing 0 80 100 100 100 100 90 90 100
    Ataxia 0 10 25 35 20 60 55 60 55
    Righting response 0 20 10 25 35 55 60 55 60
    Muscle excitation 0d 65a 60a 60a 40b 30c 45b 40b 20c
    Clonic movement 0 95 100 100 100 100 100 100 100
    Gasping 0 90 100 100 100 100 100 90 95
    Neonate pigs
    Standing and locomotion 100 100 100 100 100 100 100 100
    Oral nasal, all 90 0 15 25 15 55 45 35
    Licking and chewing 5 0 30 30 20 25 40 30
    Escape attempts 10 5 0 0 0 5 0 0
    Defecation 30 20 25 25 10 20 30 30
    Urination 20 20 35 25 20 15 30 30
    Salivation 5 5 10 5 10 5 5 5
    Nasal discharge 5 0 0 5 5 0 0 15
    Open-mouth breathing 5 90 90 100 100 100 100 100
    Ataxia 0 95 100 100 100 100 100 100
    Righting response 0 50 50 60 25 65 45 60
    Muscle excitation 0 10 5 0 0 15 0 0
    Clonic movement 0 90 100 85 85 100 100 95
    Gasping 0 90 100 100 100 100 100 90
a–dWithin a row, prevalences of pigs (%) lacking a common superscript letter differ (P < 0.05).
1Refer to Table 3 for a description of each behavior.
2AMB = pigs euthanized by blunt-force trauma after being placed in the box for 10 min.
3Prefill = pigs placed in box prefilled with the appropriate gas followed by a gas flow of 20% box volume/min; Fast = gas flow rate of 50% box volume/min; Medium = gas flow rate of 35% box volume/min; and Slow = gas flow rate of 20% box volume/min.



View Full Table | Close Full ViewTable 6.

Effect of euthanasia method on the mean latency ± SE (seconds) of weaned and neonate pigs displaying behavioral indicators of distress

 
Distress measures,1 s AMB2 100% CO2 gas3
50:50 CO2 and argon gas mixture (50:50)3
SEM
Prefill Fast Medium Slow Prefill Fast Medium Slow
Weaned pigs
Open-mouth breathing 11d 55c 59c 87b 28d 65c 86b 113a 33
Loss of posture 35e 89d 102d 143c 90d 148c 174b 238a 7
Last movement 221e 269e 274e 313b 529b 451c 297d 467b 775a,4 40
Neonate pigs
Open-mouth breathing 7c 45b 54b 67a 12c 55b 61b 33
Loss of posture 21c 74b 83b 124a 46c 108b 137a 7
Last movement 313c 226d 293c 296c 427b 397b 380b 452a 40
a–eWithin a row, least squares means (±SE) lacking a common superscript letter differ (P < 0.05).
1Refer to Table 3 for a description of each behavior.
2AMB = pigs euthanized by blunt-force trauma after being placed in the box for 10 min.
3Prefill = pigs placed in box prefilled with the appropriate gas followed by a gas flow of 20% box volume/min; Fast = gas flow rate of 50% box volume/min; Medium = gas flow rate of 35% box volume/min; and Slow = gas flow rate of 20% box volume/min.
4If pigs were insensible, they were allowed to remain in the box for up to an additional 600 s.