What I am trying to find out that if the bloodline of a dog has been in sports for 5-6 generations, does dogs lose their defensive temperament i.e. temperament genes?
The only way I see it is by taking the puppy of titled parents & training him in Personal Protection/Police or Military
Short answer: you are on the right track. If all you had to go by is a pedigree of unknown dogs all with SchHIII to their name several generations back - you are right. It does not neccessarily mean that the puppy you see will have high defense drive, and training it in PP or civil defense work will give you that answer.
However it is not the stylized Schutzhund training and trials in and of itself that will have caused the loss of defense drive, but rather the choices of the breeders and their breeding goals. Some breeders only title their dogs in SchH so that they can say that they have SchH titled dogs as breeding dogs - whether the dogs have or have not defense drive is of little import to them.
Some breeders focus on breeding high-scoring performance dogs, and indeed, a preference of high prey drive for flashier performance in obedience and high prey in the protection phase will be selected for at the expense of defense drive. These are dogs that end up "all prey, no defense" in a few generations.
Then there are breeders who focus on maintaining the balance of drives to breed dogs that can actually perform the role of a police, military or personal protection, and use Schutzhund as it was intended to be used, to test the dogs under duress and threat, and select the strongest dogs to carry forward the attributes that are part of the GSD temperament and standard.
So it would be more correct to say that defense drive CAN be lost when 5-6 generations are bred with a preference of prey drive over defense, and one way to find out if it is still in a line is to test the puppies through training. However, not all pups will inherit equally the same balance of drives, and one puppy low in defense does not necessarily means that defense drive is lost, nor would one puppy high in defense indicate that defense drive is still found reliably in that line - pup could be just a fluke.
However, I don't know how many puppies from how many litters from how many lines over how many years would need to be tested and which percentage would need to show defense drive in order to come to any type of scientific conclusion.
And your question in your last post is a very different question from your first post, so I'm still confused somewhat as to what you are looking for.