We do it for our cows on the dairy but not housepets -- no, could never do a housepet.
Pinterest's evil side.
It's not a popular opinion, but I don't have a problem with it as long as the pet doesn't suffer and as long as euthenasia is recommended anyway.
For anyone who wonders, I have no pets.
Are we talking... shooting them?
My husband had to do it for one of our cats, he said it was terrible, but much better than letting her suffer. She had fallen and was seizing, apparently she had a head injury and her eyes were blown. It was just sad to watch. So he just covered her nose and mouth. She didn't even fight back, poor baby!