Any breeder who says they've had no incidences of CHD/ED in their line is either lying, ignorant, or has not been breeding long enough. Yes, we have had some cases of CHD and ED in our offspring, though rarely worse than mild (like subluxation in one hip with no changes or UAP with no changes). The occurrences are not frequent and there is no pattern that has developed. If one looks at our pedigrees carefully, one will see that our dogs are very closely linebred. If we had rampant genetic disorders in our lines, they would be appearing with great frequency and intensity because of the concentration of our bloodlines. This brings me to my main point which is, that we do not believe that CHD and ED are genetic disorders, at least not in the vast majority of the cases we see in Mastiffs. We firmly believe that these orthopedic problems are more closely related to improper nutrition and improper exercise. We feel strongly that Mastiffs have different nutritional needs than other smaller breeds, and we also believe that Mastiffs are slower in maturing and can be easily damaged while they are young by over or under exercise. Check out these links for more information on nutrition and dysplasia, and on nutrition in relation to other disorders:
The Error of the Millennium in Veterinary Medicine
Linda Arndt ~ Canine Nutritional Consultant

I strongly encourage anyone reading this page to join the Mastiffs.org discussion forum to read the threads I've linked below. You must register with a username and password to be able read them, but it's also a great place to learn about and talk about Mastiffs. These are very good discussion threads concerning testing, OFA, and reading hip films from the Mastiff discussion board on Mastiffs.org:
Why not test?
Why do we put up with OFA?
Mastiff hip films

We have come to our conclusions because of years of line breeding (We are up to 9 generations of carefully-considered line breeding currently), watching what other breeders were producing and what we were producing, and what happened when different lines were brought together. That experience, combined with OFA results that were neither consistent with each other nor with the actual x-rays, has led us to have very little faith in the testing system. We definitely do not believe that results are accurate representations of what a particular dog has a likelihood of producing in its offspring and therefore, we do not consider x-rays in our breeding program. We prefer to rely on research (looking at pedigrees, remembering the dogs behind there, and what their siblings were like, and what they produced when bred to what lines, etc.) and we make our breeding decisions accordingly. A family of radiographically sound dogs, with OFA certifications can still throw a litter of dysplastic puppies, and a family of radiographically unsound dogs can still throw a litter of radiographically sound puppies and vice versa. The Mastiff has a very small gene pool to work with and we feel very strongly that to keep this breed alive and looking and behaving like it is supposed to that the very best dogs need to be bred based on careful consideration of what lies behind them. CHD/ED will never be eliminated from this breed, not unless the nutritional and environmental issues are properly addressed and laboriously researched by the veterinary field. Too much emphasis has gone into finding a genetic tag for CHD and they are ignoring the real issue facing giant breeds today, inadequate/improper nutrition and exercise.

We've learned that OFA results do not give an accurate picture of a dog's orthopedic health, much less give an accurate indication of how a dog will produce. X-rays will pass that should have failed, and fail that should have passed, and 2 passing dogs will produce failing puppies, and 2 failing dogs will produce passing puppies. Generations of passing dogs will produce failing puppies. And, there is also a disconnect between the actual soundness of a dog and the OFA results. Some OFA Excellent dogs have been crippled, where some dysplastic dogs have had soundness and pain-free movement throughout their life. If good hips and elbows don't define soundness, then is it more ethical to breed an unsound dog with passing test results, or a sound dog with failing results? The fact that most breeders rely so heavily on OFA to decide what dogs should and shouldn't be bred because of hip/elbow results actually inhibits breeders from discovering the true cause of the problems. It has already been indicated in several studies that nutrition and exercise/lack thereof is a major cause of all sorts of orthopedic problems in dogs, though no study of the kind has of yet been done specifically on Mastiffs. We have learned from experience that the best way to produce the best Mastiffs we can is by breeding according to pedigrees (the dogs in them) -- to what we have seen produced over and over from generation to generation. We consider ancestors and their siblings, and what type of offspring the dogs produce when bred to what other lines. We look at actual physical health over the course of a lifetime. And we breed according to experience. Our line is closely line bred, and any genetic problems that might exist in our line would be prevalent and severe if it existed and was genetic in nature, because of how closely bred our line is.

We see no reason to slash down our breed's already tiny gene pool even more trying to eliminate a problem that is not rooted primarily in genetics. As a matter of fact, we think it is terrible that so many breeders are ignoring the needs of the breed and jumping for what seems to be the easy solution. A test. Your dog takes it. He passes, he can be bred. He fails, he can't (or "shouldn't") be bred. No worries beyond that. Breeders are blinding themselves to the real issue, and they are damaging the breed at the same time, because we are losing our temperaments, we are losing our breed type, and we are losing our soundness (phenotyical, that is) and we are making up little-to-no ground on the genotypic front.
 
We understand that many are not comfortable with our stand on the testing issue. Many breeders believe that one should only breed tested dogs. We respect that stand, but we do not agree with it. We breed the way we feel will best improve the breed, and that is the way we have been breeding for 30 years. We feel we have been getting consistently good results in our breeding program and we will continue with our program until we find that we are no longer consistently producing, sound, healthy, true-to-type mastiffs.

That said, if you are uncomfortable buying a puppy from a breeder who does not test, we understand. There are hundreds of Mastiff breeders out there who do, and we encourage puppy buyers to purchase from breeders who they feel most comfortable with. We do stand behind our dogs and we, of course, sell all puppies with a contract that guarantees against debilitating defects if the proper nutritional and exercise guidelines (included with the contract) are followed. We do not want anyone to buy a dog from us who is not comfortable with our breeding philosophy. As a puppy buyer, we encourage you to find a breeder whose dogs you love, who you can trust, and whose philosophy is consistent with your own--buy a dog from them, and love that dog for its entire life.

As for other disorders found in Mastiffs, we test for them when we have cause to. For example, we once bred to a dog who had PPM. At the time it had just been switched from allowing a pass on the CERF exam to a fail on the CERF exam. Because of the merits of the dog and his pedigree, and our previous experience with PPM (we felt it was caused by infection in pups before their eyes opened) we chose to breed to this dog anyway, but to have all pups in the litter CERF'd at 8 weeks. We kept the pups on antibiotics until their eyes opened, and at 8 weeks, all 8 pups in the litter CERF'd clear. We would test for PRA if our bloodlines carried the line with the mutated gene. vWD is not something we believe to even be an actual problem in Mastiffs. Thyroid conditions are obvious by their side-effects, so we only test for that if the side-effects are present. Cystinurea--we would test for if we had urination/kidney problems arise. Cardiac--if our vet detects an abnormal heartbeat, then we will have that dog screened by a cardiologist. Brucellosis--we test all of our studs before breeding, and require all bitches we breed to be tested for it.