It is not a more humane way of killing an animal - it is for religious reasons that animals are slaughtered in this way to be considered 'kosher' - it is def NOT for the benefit of the animal.
In normal slaughter houses animals are stunned (.e rendered unconcious) before their throats are cut to drain the blood.
Found this.
Jews may only eat animals and birds that have been killed by Shechitah. Shechitah is killing the animals by slitting the throat with a very sharp knife. This has been shown to be painless to the animals, as causing pain to living things is against Jewish law. The theory is that the sharp knife cuts the carotid so that the animal loses consciousness before they are able to feel pain. By the time it is possible for the animal to feel pain it is already dead. The animal must then have all the bood drained from them.
So if it was done properly it may not have caused pain.
It just doesnt sound very nice and we are not used to it but in many places it is the normal way to slaughter animals and not considered barbaric.
actually slitting the throat hasnt been proved to be painless the brain has other blood supplys (in the vertebral arterys) so not quite true but as its a religious and therefore "sacred" practice it cant be banned..thats one of the reasons animals have to be stunned in the slaughter houses..