In the case of humans this is obviously just not an issue, though, since we're perfectly capable of existing healthily without killing/eating meat/etc (in fact,

In the case of humans this is obviously just not an issue, though, since we're perfectly capable of existing healthily without killing/eating meat/etc (in fact, it's way more efficient). For other animals, I don't know that we have an obligation to provide welfare for eg spiders and butterflies beyond our own habits, but it's an interesting question.