When is a rat old enough to euthanize via CO2?

[Peter Williams]

As some of you may know I but together a littler CO2 gas chamber. I have heard that it shouldn't be used on newborns. I have some 10 day old fuzzies that need to be euthanized, and I'm wondering if you think they will go in the gas chamber as fast as a larger rat would?

[jdmls88]

why shouldnt you? it kills them either way

[Peter Williams]

We'll I've heard they're naturally resistant to hypoxia, and it would take a very long time.

[jdmls88]

ziplock them, if they are still pink or fuzzies im sure they cant bite through the bag

[rabernet]

Peter, hopefully Joanna will see this. I believe she's read about this, and up to a certain age, freezing is actually more humane than the CO2 (this is for pinkies and maybe into fuzzy stage, but I'm not sure). It does take longer for pinkies to be euthanized with a CO2 chamber than older rodents if I remember what Joanna has told me.

[lord jackel]

Up to 14 days neonates (newborns) are naturally resistant to CO2 Hypoxia...so freezing them is much quicker and more humane(but you need to use a deep freezer that has a temp below -10 degrees (most fridge/freezer units are only -4)

Hope this helps.

[lord jackel]

Here is some specific data on the correct way to use CO2 to euthanize rodents - approved by the AVMA.

Guidelines for Euthanasia of Rodents Using Carbon Dioxide
Death should be induced as painlessly and quickly as possible. CO2 inhalation is the most common method of euthanasia used at NIH for mice, rats, guinea pigs
and hamsters.

A few important aspects of this procedure are:

1. The euthanasia chamber should allow ready visibility of the animals. Do not overcrowd the
chamber: all animals in the chamber must be able to make normal postural adjustments.

2. Compressed CO2 gas in cylinders is the only recommended source of carbon dioxide as it
allows the inflow of gas to the induction chamber to be controlled. Without pre-charging
the chamber, place the animal(s) in the chamber and introduce 100% carbon dioxide at
the rate of 10-20% of the chamber volume per minute so as to optimize reduction in
distress. (For a 10-liter volume chamber, use a flow rate of approximately 1-2 liter(s) per
minute.) After the animals become unconscious, the flow rate can be increased to
minimize the time to death. Sudden exposure of conscious animals to carbon dioxide
concentrations of 70% or greater has been shown to be distressful.1

3. Animals should be left in the container until clinical death has been ensured.

4. Neonatal animals (up to 14 days of age) are resistant to the effects of CO2, therefore,
alternative methods are recommended.3 Carbon dioxide may be used for narcosis of
neonatal animals provided it is followed by another method of euthanasia (i.e. decapitation
using sharp blades).

5. If an animal is not dead following CO2 exposure, another approved method of euthanasia
(e.g. decapitation) must be added while the animal is under CO2 narcosis to assure death.
Please refer to Appendixes 1 and 2 of the 2000 Report of the AVMA Panel on Euthanasia2
for additional recommended methods.

References
1. Danneman PJ, Stein S, Walshaw SO. Humane and practical implications of using carbon
dioxide mixed with oxygen for anesthesia or euthanasia of rats. Lab Anim Sci 1997,
47:376-385.
2. AVMA Panel on Euthanasia. 2000 Report of the AVMA Panel on Euthanasia. J Am Vet
Med Assoc 2001, 218:669-696.
3. Guidelines for the Euthanasia of Mouse and Rat Fetuses and Neonates. NIH Animal Research
Advisory Committee, 2001 (see web site: http://oacu.od.nih.gov/ARAC/euthmous.htm).