Suppose I grant that pigs and dogs are self-aware to some degree, and do have thoughts about things in the future. That would provide some reason for thinking it intrinsically wrong to kill them - not absolutely wrong, but perhaps quite a serious wrong. Still, there are other animals - chickens maybe, or fish - who can feel pain but don't have any self-awareness or capacity for thinking about the future. For those animals, you haven't given me any reason why painless killing would be wrong, if other animals take their place and lead an equally good life.

Grain that is used to feed animals that end up on our tables as turkeys and hams could have gone to feed starving people.

If it is in our power to prevent something bad from happening, without thereby sacrificing anything of comparable moral importance, we ought, morally, to do it.

Dolphins are social mammals, capable of enjoying their lives. They form close bonds with other members of their group.

There are some circumstances, for example, where the newborn baby is severely disabled and where the parents think that it's better that child should not live, when killing the newborn baby is not at all wrong ... not like killing the chimpanzee would be.

Will we rise to the challenge and prove our capacity for genuine altruism by ending our ruthless exploitation of the species in our power, not because we are forced to do so by rebels or terrorists, but because we recognize that our position is morally indefensible?

I think ethics is always there; it's not always a very thoughtful or reflective ethics.