I saw a documentary about pig farming in the Netherlands once. Spends most of the film showing the happy little porkers growing up in their pen, and apart from the bit where they avoid the meat being ruined by a boarish smell, they appeared to do well enough. Then at the end most of them get sent off. It took about 4-5 seconds from being happy little porkers to getting koshered you might say
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It was humane I guess. Lets just say it inolved electricity.