Minimal Exposure Times for Irreversible Euthanasia with Carbon Dioxide in Mice and Rats
1Laboratory Animal Resource Center, School of Medicine, Indiana University, Indianapolis, IN;,
Summary
Determining irreversible euthanasia in laboratory rodents is crucial. This study found mice require at least 3 minutes, while rats need 10.5 minutes of carbon dioxide exposure to ensure death is irreversible, preventing unnecessary distress.
Area of Science:
- Veterinary Medicine
- Animal Welfare Science
- Laboratory Animal Science
Background:
- Secondary euthanasia methods are vital for irreversible death in laboratory rodents after anesthetic overdose.
- Physical euthanasia methods can cause compassion fatigue in animal care personnel.
- Existing literature on carbon dioxide (CO2) euthanasia focuses on preweanling rodents.
Purpose of the Study:
- To evaluate the minimum exposure time of adult rats and mice to 100% carbon dioxide (CO2) for irreversible euthanasia.
- To establish species-specific CO2 exposure durations to ensure humane euthanasia practices.
Main Methods:
- Adult rats (14 stocks/strains) and mice (>40 stocks/strains) were exposed to CO2 at a 50% volume per minute displacement rate for 2 minutes.
- Animals were observed for varying durations post-exposure to assess for signs of resuscitation.
- Exposure times were adjusted in 30-second increments until irreversible death was confirmed.
Main Results:
- Mice required a minimum exposure time of 3 minutes in CO2 to ensure irreversible euthanasia.
- Rats required a significantly longer minimum exposure time of 10.5 minutes in CO2 for irreversible euthanasia.
- Failure to adhere to species-specific times may lead to unsuccessful euthanasia and the need for physical methods.
Conclusions:
- Carbon dioxide can achieve irreversible euthanasia in laboratory rodents.
- Species-specific exposure times are critical for effective and humane CO2 euthanasia.
- Establishing precise CO2 exposure durations minimizes animal suffering and supports animal welfare.
