Thread: Sacrificing mice

So, one way to sacrifice mice is to deliver increasing concentrations of CO2. My question is, is this method of sacrifice likely to induce any pain or suffering in the animal or is it a gentle procedure?

Tridimity

Well, much of it is a matter of opinion, really. Even in humans, measurement of pain is difficult because it's subjective. We ask a person things like "on a scale of 1 to 10, rate the pain" and go from there. However, we obviously cannot ask an animal like a rat and get a meaningful response. The issue is further exasserbated by the fact that the end result is death, so even if we could get feedback from rats, they'd no longer be alive to provide it.

In my (admittedly less than informed) opinion, CO2 is relatively gentle, but the mode of death is ultimately hypoxia, so you go to sleep when oxygen stops getting to the brain... You're ultimately suffocating. That can be unpleasant if it takes too long, so it really depends on length of time between initiation of the euthanasia and the cessation of respiration and heartbeat.

When I was still in school more years than I have fingers ago, the preferred method was cervical dislocation. It was immediate and hence no pain was likely felt. That's just how the professors and grad students around me chose to do it, as well as a few biologists with whom I've interacted on various science fora through the years. From what I recall, the only meaningful challenge to the approach was ensuring it was done correctly. A flawed attempt at cervical dislocation will obviously cause a fair bit of pain, and most certainly far more pain than hypoxia. However, when done correctly, it is quick and immediate, and hence seems far more humane... IMO, anyway.

I haven't read through it and checked it for accuracy, but google turned up the following report which seems fairly robust and has a number of references for you to explore. Maybe it will help:

http://www.aclam.org/print/report_rodent_euth.pdf


Cheers.

Thanks inow,

Intuitively, I would have thought that sacrifice by increasing CO2 concentrations would be a similar experience to when a human suffocates to death. Indeed, one person suggested to me that it the mouse if effectively choking. By contrast, another person said that the mouse displays no evidence of being uncomfortable - it does not grasp for air or move about in discomfort etc. I therefore don't know what to believe and of course nobody can know what the mouse is actually experiencing.

I just really, really want to believe that the mouse is gently going to sleep...

Tridimity

Well, I for one do not really care what do mice fell, but it probably could be possible to see the pain level by monitoring brain activity.

Originally Posted by tridimity

I just really, really want to believe that the mouse is gently going to sleep...

There's a lot to that notion. They are, by no means, still conscious when they pass. I understand your concerns... I do. I just tend to frame the issue as a "greater good" type thing. They are specifically bred for that purpose. It's not like we're capturing them out of the wild and taking them away from their happy little families where they sit around the fireplace reading novels and playing scrabble with grandma. They're bred for this. Our focus should be on minimizing their pain... Not on taking an absolute stand in some vain attempt to never ever let them feel it. YMMV.

Neck stretching, as inow said, is the preferred method as far as I know. The problem is, that neck stretching, if done incorrectly, can cause a lot of pain. I had this discussion years ago with a prof, and he felt that when CO2 was used the mice became very stressed and panicked, not only because they are removed to a new strange location but also from the process of hypoxia, so he preferred to break the neck. I've only ever seen the necks broken though and have no direct experience with that method.

I have also heard from the veterinary doctors I work with now, that CO2 asphyxiation causes the animals to panic.

I've also heard of the use of decapitation too, but I'm not sure that's a widespread method.

I don't know about mice, but for humans, as far as I know, death by increased concentration is agonizing. That's because the actual way our system detects the danger of suffocation is by sensing for too much . So you'd feel you are choking, just as if you had a plastic bag on your head and breathed the same small volume of air in and out until it became unbreathable.

On the other hand, we do not directly sense a lack of oxygen. So if the is removed but fresh oxygen is not supplied, basically leaving you with just nitrogen, you would feel weakened and dreary but not choking. This is known as controlled atmosphere killing and has been proposed as a potential humane method of execution, although I don't think was ever approved by legislation (in any country) or actually carried out in a judicial context. Knowing the ingenuous cruelty of our race, I'd be surprised if it hasn't already happened in some less official setting.

Various species of animals have different ways of sensing inadequate breathing air, so you'll have to find out if what is true for humans is also true for mice.

All of the above are my ruminations based on random information from the media. Verify, check, double-check, and consult experts before you use any of what I said to make decisions that may affect the amount of suffering inflicted on any living creature.

Thanks for your views guys

I'm speaking from experience here:

Well, open the lid of the CO2 chamber (bucket) and see how the mice are dying.

It isn't a pretty sight. They empty their bladders, release their bowels, and gasp for air, panicking for sure. They aren't immediately dead.

Cervical dislocation seems a lot faster, but it requires some skill.

And then there are mice pups. The ones I have been dealing with.

They don't respond to CO2. You have to do cervical dislocation, but they are too small usually for the regular method. So you end up cutting up their heads instead with sharp scissors.


No method is pretty. It's all quite grisly. Maybe that is good because I kill as little mice as I can just for this reason.

CO2 method:

there are basically two ways: Either you pre-fill the chamber with CO2 and dump the mice in there: panic guaranteed. But they die a bit sooner.

Or you put the mice first in the chamber, let them relax a bit and then open the CO2. Panic also guaranteed because the influx of large amounts of CO2 is noisy.

Anyway, you need to do cervical dislocation after CO2'ing them anyway, to make sure they are dead and don't revive suddenly in the biowaste bag.