For those who are vegetarians and offer ethical reasons (animals are slaughtered under the most brutal conditions) against meat eating, genetic engineering comes to the rescue with reports that animals can be genetically engineered to feel no pain during slaughter...
Recent advances suggest it may soon be possible to genetically engineer livestock so that they suffer much less. This prospect stems from a new understanding of how mammals sense pain. The brain, it turns out, has two separate pathways for perceiving pain: a sensory pathway that registers its location, quality (sharp, dull or burning, for example) and intensity, and a so-called affective pathway that senses the pain’s unpleasantness.
This second pathway appears to be associated with activation of the brain’s anterior cingulate cortex, because people who have suffered damage to this part of the brain still feel pain but no longer find it unpleasant. .. Recently, scientists have learned to genetically engineer animals so that they lack certain proteins that are important to the operation of the anterior cingulate cortex. Prof. Min Zhuo and his colleagues at the University of Toronto, for example, have bred mice lacking enzymes that operate in affective pain pathways. When these mice encounter a painful stimulus, they withdraw their paws normally, but they do not become hypersensitive to a subsequent painful stimulus, as ordinary mice do.