Hi I work in a pet store and study dog and cat nutrition at work and at home. Duck is a cooling protein that helps with inflammation but so is whitefish, alligator, red snapper, and there are a few others as well. As far as your concern with DCM; it is a topic that I am very wildly knowledgeable in and talk to many customers about. I recommend reading the whole FDA article or at least skimming through it. There are two documents, one is all the cases and one is the FDA’s study. The results are inconclusive at the moment and many brands are working together with the FDA to further investigate.
From reading it I can tell that there are many factors that the FDA left out like affordability (who can afford the vet bills for these tests? What food are they feeding if they can afford? Are they feeding a more expensive kibble or a cheap one at Walmart?), genetics (what breeds are more likely to have which diseases? How many of this species is in the USA (out of 77 million dogs), metabolism (how can a dog digest a kibble diet compared to dehydrated, canned, freeze dried, or raw? How bioavailable is taurine in kibble?), what diets were these dogs on (a majority were on kibble only, some had a mixture, I think 1 or 2 were on raw, and couple had dehydrated foods).
In the end, out of the 500 some cases of dogs with DCM a huge section were fed kibble only diets. So, if anything I would link it more so as a kibble problem than a grain free vs with grains. With the research I have done looking at scholar articles, brand studies (of course always reading between the lines because brands what to do a study to help their brands cause), blogs, and websites, I have noticed that grains cause more inflammation in dogs than peas as they are not as easy for dogs to digest. They force the organs to work a little bit harder. If you notice too, no raw diets (at least that I have come across) have grains in them, only fruits and vegetable, and meat.
But if you do decide to feed grains. Please watch out for smelly ears, itching, and hot spots. As grains, along with chicken, are a very common allergy in dogs (since they are put into a lot of foods due to their low cost).
