I think it is a common problem, actually.

I know one kid, a college sophmore, who had never seen a cow until he was 18, and didn't realise that is where we get milk from. I didn't bother to point out to him that where he goes to school, if a cow is no longer producing milk, she goes to the little barn, then to the dining hall. I just didn't have the heart.

At least not while he was eating.