Huh, I thought those things killed the cattle rather than just stunning it. Like in No Country for Old Men.
I seriously doubt that an animal would come round from a captive bolt wound, because (with a penetrating bolt anyway) the brain is injured. However, the heart keeps beating and the brain stem goes on working so that the blood is pumped out of the carcass. The animal is also "pithed", that is a flexible rod inserted into the skull defect, right back to the brain stem. That kind of does the trick. (It's quite weird when animals killed that way come in for post mortem. The plastic rod is sticking out of the forehead, and when you cut the head off, it's there in the spinal cord.)
You can find this as nauseating as you like, that is not the point. The point is that the animal loses consciousness instantly, with no idea what hit it.
Ironically, kosher slaughter was originally designed to achieve the same aims. Down the animal quickly and allow it to bleed out by having the heart go on beating. It was intended to be humane, and for that time, it was humane. Compared to a lot of other stuff. The trouble is, you don't immediately black out when your throat is cut, because there is other circulation to the brain.
Actually, halal slaughter isn't so bad as shechita, because the animal is supposed to be immediately decapitated, like a guillotine, but using a sword. This gets all the cerebral circulation and unconsciousness is a lot quicker. When it goes right. I don't know the percentage, but it's a very difficult thing to get right, and keep getting right time after time as your sword begins to get blunt and your arm starts to get tired. I don't think it was ever originally designed to be used in slaughterhouse conditions where many animals have to be killed one after the other.
There's no problem about doing these ritual slaughtering methods after the captive bolt is used. Except people who don't understand that their religious texts are just best practice from many hundreds or thousands of years ago, enshrined in religious writings as a good way to keep people doing what they were instructed to do.
"It is not possible to improve on the wisdom of Abraham," was the reply my meat inspection lecturer got when he raised the matter with the chief rabbi. Meanwhile, generations of Jewish vet students do their meat inspection practicals, and go home and have blazing rows with their parents. Apart from the few who are really fundamentalist about it, who set about writing apologetics that look scientific, to try to fend off criticism.
It's my belief that in countries where slaughter without pre-stunning is illegal, the Jewish communities somehow find they can live with this. If that's the case, it's time a few more communities wised up.
Rolfe.