Man, I remember carrying a veal calf in a wheelbarrow away from it's grieving mother (who ended up distressed for days) when I was 16 doing some Summer farm work. It messed me up for weeks, and I still somehow went back to drinking dairy. Thankfully I've sworn off all animal products now, but the knowing cruelty of it I suppressed for a long time.

I've heard several people say fish don't feel pain. Makes hobby fishing seem less cruel I guess.