You are narrowing your search too far. Just research “dog diet for liver disease” or better yet, “low copper diet for dogs”. There are dog foods for dogs with liver issues.
Are you also supplementing periodically with a high quality vitamin B complex as well as E, K and C? Although it is risky to give zinc all of the time, it is a good binder for copper.
You can also provide turkey and chicken but NOT duck. We use hard boiled eggs which are put into a food processor (or blender) and ground up, shell and all because calcium is a good phosphorus binder and eggs are an excellent protein source. I also supplement magnesium for my kidney disease dog to balance the calcium.
