I'm a butcher who works in a slaughterhouse. Pigs are lowered into the co2 chamber, and then raised up after a minute and they've passed out, then you poke their eyeball to ensure they're asleep. Wrap a chain around their hind leg and host them upright, you stick them in the throat on both sides and they bleed out, dying almost instantly, they gently swing around a corner, spraying the backsplash with remaining blood and then they go through a massive burner... A flamethrower of sorts. After the flamethrower they're lowered onto a table and the chain is removed and they're dunked into a massive vat of boiling water. They're hooked through the Achilles and hoisted back up... I could keep going but the point is, these hogs only squeal on their way into the gas chamber because they don't like being told what to do.