Will My CO2 Chamber Kill Hatchling Balls Too?

[satomi325]

Ok. I've been on vacation without a pc and internet access till now.
If more sources are needed, I can find more.

Nitrogen, argon(a noble gas), and CO may be acceptable for euthanasia, but according to the University of Texas, "there is no clear advantages, which is why they are rarely if ever used."
If they and the other gases you listed were more effective and humane, then CO2 wouldn't be the standard gas of choice for euthanasia.
I work in a laboratory at one of the top research universities, not to mention the number one veterinary school in the US. I have euthanized a vast amount of rodents in the lab and at home with my own personal feeder colony. I have seen and done this first hand. CO2 is humane if administered correctly. Please refer to the IACUC and AVMA protocols for responsible euthanasia use. CO2 isn't used based on 'tradition'. CO2 isn't used just because it is fast. Euthanasia doesn't mean fast. Euthanasia is the act of inducing humane death in an animal by a method that induces rapid loss of consciousness and death with a minimum of pain, discomfort or distress..... It's used because it has been proven as humane method of euthanasia. (Equal or more so than other gases. However, they can be used in combination with CO2.)

Some studies that show adverse effects of Nitrogen/Argon euthanasia:

Our study indicates that rats are averse to argon-induced hypoxia over a range of flow rates, and the physiological effects of hypoxia become aversive at approximately 7.7% O2. These results suggest that argon is not a suitable alternative to CO2 for the euthanasia of rats.

I. Joanna Makowska, Lee Niel, Richard D. Kirkden, Daniel M. Weary, Rats show aversion to argon-induced hypoxia, Applied Animal Behaviour Science, Volume 114, Issues 3–4, 1 December 2008, Pages 572-581, ISSN 0168-1591, 10.1016/j.applanim.2008.04.005.

Specific behaviors were observed that might relate directly to pain and distress during gas exposure. No rats in either the argon or CO2 treatment group showed any obvious escape behaviors during gas exposure. Shaking occurred in 3 animals during the baseline period and in one animal from the argon treatment group during gas exposure. Grooming of the face was observed in one animal during CO2 exposure and in 2 animals during argon exposure. During argon exposure, rats showed adverse behaviors before they appeared to lose consciousness. All of the argon-exposed rats showed hyperreflexia or seizures; these occurred both before and after recumbency without tone. In addition, 3 of 7 argon-exposed rats showed back arching with an open mouth, which was termed abnormal gasping. This behavior always occurred before recumbency without tone.

Burkholder TH, Niel L, Weed JL, Brinster LR, Bacher JD, Foltz CJ. 2010. Comparison of carbon dioxide and argon euthanasia: effects on behavior, heart rate, and respiratory lesions in rats. J Am Assoc Lab Anim Sci 49:448–453.

It has been proposed that Ar is superior to CO2 because it is not irritating to animals and therefore does not produce distress. However, we observed that approximately 100% Ar produced significant increases in MAP within the 1st minute of exposure suggesting that exposure to high concentrations of Ar may be stressful. In fact, the severe hypoxia or anoxia resulting from breathing 100% Ar is expected to be stressful. If this expectation is true, then exposure to approximately 100% N2, which also is expected to produce severe hypoxia or anoxia, likely is equally stressful

(MAP, mean arterial blood pressure)
According to the Journal of the American Association for Laboratory Animal Science, Volume 45, Number 2, March 2006 , pp. 21-25(5), they say that CO2 is effective for inducing unconsciousness and euthanasia. Ar appeared to be effective, but produced hyperflexia and tachycardia effects. They also concluded that N2 is not satisfactory for euthanizing rats or inducing unconsciousness in them.


Studies that show CO2 with no adverse effects:

Our results showed more rapid falls in pulse rate and blood pressure in rats euthanized in a chamber precharged with carbon dioxide (CO2), when compared with rats euthanized more slowly, but death still took over 5 min in the former group. There was no behavioral evidence of pain or distress in either group during euthanasia.

Smith W, Harrap SB. 1997. Behavioural and cardiovascular responses of rats to euthanasia using carbon dioxide gas. Lab Anim 31:337–346. [PubMed]

A method of inducing euthanasia by carbon dioxide (CO2) inhalation in the home cage of an animal is described and tested for distress by behavioural as well as by hormonal measures. There were no signs of distress by behavioural or by hormonal changes.

Hackbarth H., Küppers N., Bohnet W. (2000). Euthanasia of rats with carbon dioxide – animal welfare aspects. Lab. Anim. 34, 91–96. doi: 10.1258/002367700780578055. [PubMed]


And another note, I've inhaled nitrous oxide for an oral surgery. It's probably a personal thing, but it did nothing for me. :\