The Science of Humane Slaughter
I asked an expert on humane livestock slaughter how we decided on certain methods of slaughter as more or less humane than others, from a scientific perspective.
He pointed me to this document (PDF) from the European Food Safety Authority called
“WELFARE ASPECTS OF ANIMAL STUNNING AND KILLING METHODS:”
Scientific Report of the Scientific Panel for Animal Health and Welfare on a request from the Commission related to welfare aspects of animal stunning and killing methods.
It's long, and old (from 2004) but it's a pretty useful document summarizing a lot of the science of why certain methods of killing may be more or less humane.
You can test a method, for example, by hooking an animal up to an EEG and monitoring its brainwaves after stunning it, or delivering a fatal blow (functionally killing it, but it won't always die instantly following a fatal injury, so you can still monitor it.)
Other ways of monitoring and measuring suffering include recording: how many times does an animal vocalize (moo, grunt etc) after being put in a chute? If it moves, does that matter, or is that a post-mortem or unconscious spasm? Does it immediately collapse, does it blink when you touch its eye (corneal reflex)? Is the animal permanently brain-damaged (which is a good thing when you want it to die fast!) or is it only a little knocked out and immobile, with the potential for recovery if you were to not bleed it out? (Which is bad in that circumstance!) A scientist can test that by testing a stunning method on a group of animals and then seeing if they recover. Those individual animals are likely not happy if they do return to consciousness with a hole in their heads, but such is science.
Anyway, while the testing might sound gruesome, I thought you'd like to know that slaughter regulations are pretty serious and well-studied. And those regulations seem pretty consistent among everywhere I've seen (EU, Norway specifically, the US.) With some minor differences here and there.
Perhaps we will discover better ways to slaughter meat animals in regard to their welfare, or perhaps we will find one day that our preferred method wasn't as good as we thought! There might also be people doing things in very bad, unintentionally cruel ways because of silly, disproven myths (but, if someone is legally selling meat, any US slaughterhouse is required to have a USDA rep see every death.)
I don't want to imply that every animal death goes perfectly well, or that it's even acceptable, or that the meat industry is perfect or good! But I do want to share that there is scientific precedent for why people kill livestock the ways they do, and you can read the studies in the aforementioned document. There are tons.
PS. If you have any interesting insights on the science of humane slaughter, I'd love to see them! Or, even, just tell me how it's done in your country, the role of the government, etc.