I agree - there's a big difference between the ability of various species to experience suffering or to experience happiness, and I think that has an impact on the ethics of how we treat them. Humans, monkeys, pigs, dogs, etc. are definitely social/emotional intelligences that deserve better treatment than we give them. Rats? Chickens? Insects? Jellyfish? Plants? Bacteria? Somewhere on that spectrum I cease to worry about the suffering of the animal and worry more about those affected by it.