I only read the intro post, not all the replies. I own APBT, always have, always will. I see different types of DA in all the dogs I have (I have 7). Some exhibit DA to animals on the other side of the fence, but if the animals are brought inside the house, they do nothing. Some have high prey drive and will kill any animal regardless, in the yard. Not in my house. If I go to the vet, he comes to the car to see my dogs, DA in the office. Dog shows, they have to be kept on a very short lead, next to me. God forbid I watch any tv show with an animal. Nothing like a $1200 Plasma crashing to the floor!
All my dogs show signs of DA/or just plain animal aggression.
There is a difference in many I have seen. Many American Bullies do not exhibit DA, for many generations, then one or two will.
Prey drive is something as well, that has to do with DA I believe, and can be confused easily.
I do not believe DA can be bred out of a line that is known for exhibiting DA. I don believe it is a simple genetic disorder. In many breeds, especially the APBT it is part of what the breed actually is. It would be as hard to erase as say, their instinct to pant-
I do not believe that DA can be erased in a genetic pattern such as breeding out something like an overbite, kink tail, or skin disorder. It is not a recessive gene. It falls more on the "instinct" side of the breed in question.
DA can be controlled, but never ever trusted.