pain and distress during co2 euthanasia
TRANSCRIPT
Joanna Makowska
UBC Animal Welfare ProgramTHE UNIVERSITY OFBRITISHCOLUMBIA
THE UNIVERSITY OFBRITISHCOLUMBIA
ANSC 500
March 3rd 2008
In Canada, over 2.5 million laboratory animals used in 2006
332,000 rats (13%)911,000 mice (36%)
UBC Animal Welfare Program
The most frequent laboratory procedure
Most common for rodents: CO2 2 methods:
Pre-fill Gradual-fill
UBC Animal Welfare Program
UBC Animal Welfare Program
Definition:
Greek “eu” = good and “thanatos” = death
Killing animals without pain or distress
Welfare implications
Key questions:
1)Does CO2 euthanasia cause PAIN?
2)Does it cause DISTRESS?
UBC Animal Welfare Program
Humans: pain at > 40% CO2 Rats: activation of nasal nociceptors at > 40%
CO2
CO2 converted to carbonic acid in mucosa
Acid causes burning sensation
CO2 + H2O H+ + HCO3-
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Humans: nasal irritants cause bradycardia
(slow heart rate) at >40%
Does it occur during CO2 euthanasia?
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Rats exposed to: Pre-fill (100% CO2) Gradual-fill (20% chamber
volume/min)
Recorded: EEG (brain activity) ECG (heart activity)
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Golledge et al. 2005
UBC Animal Welfare Program
Bradycardia
Unconsciousness Death
Golledge et al. 2005
Potential for 10 sec of pain
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BradycardiaUnconsciousness Death
Golledge et al. 2005
No pain
Key questions:
1)Does CO2 euthanasia cause PAIN?
2)Does it cause DISTRESS?
UBC Animal Welfare Program
Behavioural responses to CO2:
Nose to lid contact Rears Escape behaviours Vocalizations
UBC Animal Welfare Program
UBC Animal Welfare Program
Niel & Weary 2006
(Video of a rat’s behaviouralresponse to CO2)
UBC Animal Welfare Program
Niel & Weary 2006
Compares motivation for a reward against motivation to avoid gas exposure
UBC Animal Welfare Program
UBC Animal Welfare Program
(Video of a rat running the task)
Rats exposed to: Pre-fill Gradual-fill
Recorded: Time to leave the test cage CO2 concentration when left the test cage
UBC Animal Welfare Program
Niel & Weary 2007
UBC Animal Welfare Program
Niel & Weary 2007
UBC Animal Welfare Program
Niel & Weary 2007
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Carbon dioxide
(%)
Flow rate (%/min)
Behavioural responses Escape behaviours begin at 10% and peak
at 20% Loss of consciousness at >30%
Approach-avoidance testing CO2 exposure is aversive to rats, starting at 15%
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Dyspnea is a discomfort caused by the urge to breathe In humans, starts at 7% CO2 Severe at 15-20% CO2
Consistent with rats’ aversion thresholds
UBC Animal Welfare Program
UBC Animal Welfare Program UBC Animal Welfare Program
High CO2 causes pain
Low CO2 causes distress (dyspnea?)
ALTERNATIVES ARE URGENTLY NEEDED
Any questions?