NOT EXACTLY MY VISION (ABOVE) BUT IT COULD WORK.
In the future meat could be developed without the use of killing an animal with a brain. This organism would be a mutated form of a animal (cow, chicken, duck etc) that would develop without the ability to feel pain because only the brain stem would work. It would enable the organism to grow but function as a plant does. Would the killing of this organism like the killing of spinach be acceptable to the vegetarian or would their be another justification not to eat it?