If you guys are considering raising mice/rats for your cats, how would you go about killing them for dinner? If ever consider it, I want to be as humane as possible, of course.
I would use CO2, which is probably the most common method. If done correctly, it is supposed to be humane. It is also one of the few legal options in my area, and it is also very effective for killing a larger amount of animals. You simply put the mice in a container, and then add CO2.
There is some controversy to the method though, like how they are technically suffocating, which doesn't sound very humane. But plenty of people claim that if CO2 is added slowly, then they will pass out before they realise what is happening.
There are plenty of ways to find pressurized CO2 to use for this, like using paintball canisters or CO2 bicycle pumps. I have experimented with small CO2 systems for my aquariums, so I already have everything I need at home.