This morning I looked out of my kitchen window and saw a falcon picking apart a small animal (bird I think). It took an incredibly long time for the animal to stop moving. That's death in nature. We can and should strive to do better.
All animals should only be allowed to be raised in captivity and killed as humanely as possible.
And from there it follows that we must capture and enslave all humans, to prevent them from causing pain and hurting each other as they would given their own devices.
There is a fantasy series with this motif. It's called The Second Apocalypse, by R. Scott Bakker, and the first book is called the Prince of Nothing.