I remember we had what I thought was a pretty cool pig when I was a really young kid, sorta like outdoor pet pig. My dad and uncle took me one night out to load him up in to the pickup, (I was probably 5 or 6) running it thru the gambit in the stalls, and gave me a spade shovel, and told me to "wack it" up into the tailgate, if it tried to get by me. When I promptly smacked him with the shovel in the face, and he ran up the ramp, and up into the truck bed.
Once he arrived back at the house headed for the deep freezer.
I never quite looked at the meat on my plate, in quite the same way.
I've done a lot of hunting and fishing since then, and seen hundreds, probably thousands of dying and/or dead people over my life. I once helped assist a doctor with a "conscious" surgery while it was performed. (patient screaming with thier intestines exposed, had terrible internal bleeding and blood clots). It's pretty simple to condition oneself to become indifferent to the suffering of another living being, (at least for me anyhow) and I think humans do this better than any other species.