My horse goes ape for human food, but I REALLY limit what she has. She's also got an iron gut, I don't think I could make her colic if I tried. :roll: The things that animal has consumed would make most people gasp in shock.
I mean, the obvious answer is no, do not feed your horse chocolate. Same as dogs, in sufficent amounts, the ingrediant theobromine can be toxic to them. However, I do feed my mare junior mints (small chocolate cover mints) occasionally as a treat because she loves them, and I've never had a problem. She's also stolen chocolate bars from unsuspecting children before, so I have to watch her like a hawk at shows and stuff. But again, I've owned her since she was born and I know she's gotten into things she should never eat and she's never had issues, so a chocolate mint once every six months isn't going to kill her. Is it the same for other horses? I think I may be nervous to try if the horse is completely unused to human food of any sort.
However, I honestly do not see a small nibble of chocolate being dangerous for any animal. But that's my opinion, it really is a judgement call.