Hi,
If the father is tested clear for AMS and FN, then those conditions cannot be passed on to any of his offspring i.e. they won't develop either condition. However, if the mother carries either of these, some of the pups could be carriers. So with one parent tested clear you have a guarantee that the puppies won't suffer from the diseases but could still be carriers so could pass the carrier status on to any progeny (or even affected status if the other parent was also a carrier. Hope that makes sense? (My middle dog's sire was tested, but dam not. I was happy with that as I hadn't intended to breed, and didn't want to discount pups/lines I liked just because both parents weren't tested. Am happy knowing he won't develop the diseases). Hereditary clear pups will come from 2 tested parents (so won't need testing prior to breeding to prove their status).