I'm inclined to agree with you, Sandra,I think something is missing if Cody is eating dirt. Mine dig in the dirt and of course, bring it inside, but I've never seen it eaten. Could you add some kind of oil to her diet (fatty acids have lots of fish oil) or something to help everything come through better?
I think you need to do exactly what you are doing and ask the question to people who might know the answer. I'll post in on the Golden Retriever site on MSN too and see if I can get a good answer for you.