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Comment by albrewer | Hacker News Reader

Why not suffocate them with nitrogen or co2 or something?

Everyone agrees drowning is really not humane but nitrogen isn't approved either (rodents are not humans and so they might react to things like inert gas hypoxia differently).

CO2 is common in labs though lab rats/mice do show aversion to CO2 which is interpreted to mean that it causes distress. So there's been ongoing debate for 20+ years over how humane CO2 is and what the correct flow rate should be and if oxygen should be added (or not) or other gasses (or not).[1]

Something physical like direct concussion/blunt force trauma followed up by another method might be better[2] (needs more studying) but there's also issues with physical methods because they require more skill to do correctly (or tools/machines developed to negate the skill factor).

Also operators dislike physical methods compared to gassing[1] so what's most practical might end up the standard[3] even if it may not be the most humane.

I mean, theoretically if you could instantly crush a mouse, faster than brain/nerve signals can travel, that would be humane, right? But then a human has to deal with a gruesome crushed mouse.

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5035945/

[2] https://journals.sagepub.com/doi/full/10.1177/00236772221097...

[3] https://www.avma.org/sites/default/files/2020-02/Guidelines-...

20 years ago I worked in a place that killed them with acetone, covering the mice with a lab paper then wetting the paper with about 50 ml acetone per 50 animals and closing the lid. It was fast.

My daughter got an internship at a research lab this summer - where they have thousands and thousands of research mice and they kill several mice every day. She said CO2 works on adults and therefore that's what they use. But CO2 doesn't work on baby mice and is considered inhumane. Instead they use scissors and cut off the baby mice's heads. It's to be done swiftly so it's like a guillotine. The labs are continually monitored to ensure the animals are stressed as little as possible.

I'm curious why the CO2 doesn't work on the babies. Is their rate of breathing just much slower?

> they use scissors and cut off the baby mice's heads. It's to be done swiftly so it's like a guillotine.

Yes, that sounds fine. Much more humane. Carry on.

As long as the ethics committee OKs it.

It sounds like they had put some thought into which methods cause the least suffering. It doesn't sound like they were trying to skirt the edge of what the ethics committee would allow, which is how I read your comment. Please let me know if I have misinterpreted.

As to possible alternative methods, those include freezing, which could be quite prolonged and painful, and blunt force trauma, which could be difficult/ambiguous to perform correctly and confirm correctness every time.

Your assumption is that the mice must die.

Given that its the case, you then wonder about the most effective means of killing them.

But, pushing back on your assumption, what value can there possibly be in killing baby mice?

Feeding snakes?

at the research lab?

Why not have research snakes? And a research mongoose to eat the research snakes? And research jackals to eat the research mongoose? And research lions to...

Do you mean in general? There are two reasons given in this thread: medical research and pet (snake) food.

I expect I don't need to explain why it's best to kill the mice humanely for medical research which involve dissection of some sort.

For snake food, it's best to feed mice that have been euthanized. Feeding live mice is cruel to the mice, who experience terror right before death, and there is also the possibility that a struggling mice could injure the snake.

Absolutely - this is a world-renowned medical research school and since they always have interns you can expect this question has been asked many, many times. They feel the need to explain it in their orientation because they know some of the students are going to be shocked by the procedure.

My daughter did say it's done so fast and the mice are so accustomed to being handled there doesn't appear to be any fear on the mouse's part and there doesn't appear to be any suffering, let alone needless suffering.

Funny anecdote - the first time she was in the lab when they were doing this she hadn't had breakfast that day and had a light dinner the night before and she fainted from low blood sugar. Took her a couple of days to convince them no, she was fine, she just let her blood sugar get too low.

> But CO2 doesn't work on baby mice and is considered inhumane.

> Instead they use scissors and [swiftly]

oh snap!

Mice must have a high nervous conductance rate and as small as they are, what do you reckon how quickly it had to go through for there to be no impulse to speak of? (ask her!)

$5 Home Depot bucket

$189 nitrogen gas tank

Plus any regulatory, liability, etc. issues that go along with having & regularly using stuff that could also suffocate your employees.

The things franchise owners will do to save pennies.

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