The document discusses the UBC Animal Welfare Program's examination of CO2 euthanasia methods for laboratory rodents, revealing potential pain and distress associated with high CO2 levels. Key findings indicate that rats experience adverse behavioral responses and aversion to CO2 concentrations starting at 15%. The text highlights the need for alternative euthanasia methods due to the identified welfare implications.

1. Joanna Makowska UBC Animal Welfare Program ANSC 500 March 3 rd 2008

2. In Canada, over 2.5 million laboratory animals used in 2006 332,000 rats (13%) 911,000 mice (36%) UBC Animal Welfare Program

3. The most frequent laboratory procedure Most common for rodents: CO2 2 methods : Pre-fill Gradual-fill UBC Animal Welfare Program

4. Definition: Greek “eu” = good and “thanatos” = death Killing animals without pain or distress Welfare implications UBC Animal Welfare Program

5. Key questions: Does CO2 euthanasia cause PAIN? Does it cause DISTRESS? UBC Animal Welfare Program

6. Humans: pain at > 40% CO2 Rats: activation of nasal nociceptors at > 40% CO2 CO2 converted to carbonic acid in mucosa Acid causes burning sensation CO 2 + H 2 O  H + + HCO 3 - UBC Animal Welfare Program

7. Humans: nasal irritants cause bradycardia (slow heart rate) at >40% Does it occur during CO2 euthanasia? UBC Animal Welfare Program

8. Rats exposed to: Pre-fill (100% CO2) Gradual-fill (20% chamber volume/min) Recorded: EEG (brain activity) ECG (heart activity) UBC Animal Welfare Program Golledge et al. 2005

9. UBC Animal Welfare Program Bradycardia Unconsciousness Death Golledge et al. 2005  Potential for 10 sec of pain

10. UBC Animal Welfare Program Bradycardia Unconsciousness Death Golledge et al. 2005  No pain

11. Key questions: Does CO2 euthanasia cause PAIN? Does it cause DISTRESS? UBC Animal Welfare Program

12. Behavioural responses to CO2: Nose to lid contact Rears Escape behaviours Vocalizations UBC Animal Welfare Program

13. (Video of a rat’s behavioural response to CO2) UBC Animal Welfare Program Niel & Weary 2006

14. Niel & Weary 2006 UBC Animal Welfare Program

15. Compares motivation for a reward against motivation to avoid gas exposure UBC Animal Welfare Program

16. (Video of a rat running the task) UBC Animal Welfare Program

17. Rats exposed to: Pre-fill Gradual-fill Recorded: Time to leave the test cage CO2 concentration when left the test cage Niel & Weary 2007 UBC Animal Welfare Program

18. UBC Animal Welfare Program Niel & Weary 2007

19. UBC Animal Welfare Program Niel & Weary 2007 17 Carbon dioxide (%) Flow rate (%/min)

20. 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% UBC Animal Welfare Program

21. 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

22. High CO2 causes pain Low CO2 causes distress (dyspnea?) ALTERNATIVES ARE URGENTLY NEEDED UBC Animal Welfare Program UBC Animal Welfare Program

23. Any questions?