Sentience is hard to measure though. Also I had a weird discussion with my neighbour once who argued that in order to kill fewer sentient beings, we should eat the bigger ones as the ratio of meat per sentience was better, so we should really eat whales. Which made it pretty obvious to me that a) he was nuts and b) sentience might not be the best indicator for ethic food consumption.

/edit That doesn’t mean that I oppose the idea that eating plants is better. I’m just arguing against sentience as a good indicator.