How many people can truly say that they have fed the same dog food to all of their dogs since they had dogs and every one of their dogs has been "perfect" on it?
You need to define perfect Wolfsoul. Not to stray too far from the thread subject... would I consider my little Barney's coat perfect? No, it has a little dander, probably left over from his puppy Demodex mange days almost 4 yrs ago. It doesn't seem to bother him, and his coat still shines. As I watched him this morning chasing like wild after a Bunny down my driveway (I had to step aside to keep the terrified Bunny from literally running into me with my little monster in pursuit), it isn't too difficult to figure out he is getting enough energy and vitality out of his diet. He has no identified health problems. Neither does his older sister. Not sure if that defines perfect, but it does define healthy. Both have been on the same brand of dog food all their lives, the same brand I fed my previous dog of 11 years.

My previous dog had allergies to something in the Fall environment. Probably leaf mold was a good candidate. Chewed on her paws a little. What I commonly read on forums (not just this one) are people talking about switching foods, and how it takes time to purge the previous food's toxicity from their bodies. They usually speak in terms of months. So if I had switched diets, and observed my dog's allergies had cleared up in 3 months, it might be easy to assume it was a food allergy. Of course that leaf mold has sort of also cleared up in that time period. Then next year the allergy returns, and yet another food try. Quickly one could jump into the domain of saying one's dog was allergic to many dog foods, or had a sensitive tummy. That's not to say there are dogs without true food allergies. But rather there is a higher incidence of us humans jumping to that conclusion. Also the more foods tried, the more likely it is a food allergy (not to mention digestive problems) will be encountered.

Back to the thread... It's my belief there are very few breeders if any that are addressing the problem of genetically linked cancer in our dogs. Goldens have a high incidence of Hemangiosarcoma, and Lymphoma. Labs have a high incidence of Lymphoma. My poor Daisy 1/2 of each of those two breeds was like a walking Lymphoma time bomb- that did go off at 10 yrs of age. Not even hybrid vigor could prevent it. If you want a definition of perfect health, she was it (leaf mold allergy not withstanding), up to the point of diagnosis. She lasted 1 yr and 3 days. The big C problem will get worse in future years. Maybe after we humans create a genetic disaster in our dogs via breeding practices, something will be done?