I used to give my dogs "leftovers" such as a small piece of steak. I had to learn my lesson the hard way. I had a black lab that I fed some leftover pieces of meat to. The dog got REALLY sick and ended up having to stay a couple of nights at the vets.
When the dog was ready to come home, it was recommended that I only feed her the higher end dog food.
Ever since that problem - no table scraps for my dogs.