All arguments in favour of Vegetarianism and contra The Debate on the Joy of Fish" (知魚之樂) : In this anecdote, Zhuang Zhou argued with his fellow philosopher Hui Shi whether they knew the fish in the pond were happy or not, and Zhuang Zhou made the famous observation that "You are not I. How do you know that I do not know that the fish are happy?" (Autumn Floods 秋水篇, Zhuangzi). — Wikipedia
We don't know whether animal sentience is comparable to human sentience. That, however, doesn't mean we can't make an educated guess.
Is sentience the deciding factor though? Should we follow Mill's footsteps and utilize
nociception as the gold standard for judging ethical
pragmata?
If I'm permitted to kill a chimpanzee, feast on its meat and a chimpanzee is only 0.01% different from us genetically, can a species 0.01% above us, DNA-wise, do the same to us? Perhaps there's some kind of threshold of intelligence beyond which predation is impermissible and we've defintely reached that point, perhaps progressed beyond it, oui mes amies?