The entire concept can become more inflated dependent upon the environment.
Take the Eskimos for an example. When the would bear a child if that child was in any way lacking, or even a female, they would often just take the newborn and set it out side to freeze. that is an extreme case but you can see how any example along those lines can further enhance our reasoning or our ability to show compassion.

Nice political punch Ne-yo

Solskye, Did you just make that up as you were writing?
I don't really follow you. God I can't stand the whole objective subjective argument.
With out the ability to reason, changes the entire thing. Aside from administering any pain of coarse, an animal does not have the ability to comprehend or have any precognitive or preconceived notion of death.
It is us humans that feel the pain, emotionally. Yet we somehow turn it around at focus the attention away from that, therefore it is again justifiable.