Traits that would be deadly if the animal wasn't in captivity??

How about brachiocephalic noses (pug, boxer, Persian)? Or any albino animal? Or hairless dogs/cats/rats/guinea pigs/hamsters/mice? Or super short legs in an animal that was once a carnivore? Or miniature animals? Or crummy teeth?

There are loads of traits we breed into animals that make them totally unfit for life in the wild. That's why we call them 'domesticated' animals.

I like the fainting goats. It's a neat trait, it doesn't seem to bother them at all, and it once served a useful purpose.