Someone once told me all dogs originated from wild dogs. There is no proccessed dry foods and preservative filled proccesed meats in the wild.
The advice was animals will always do best on what their bodies were designed for. Stick to raw and meaty bones, eggs and things like flax seed oils which occur naturally in wild dog diets, the odd veggie and greenery and of course the odd wilderbeast or 2.
My son found a plant in the supermarket called "pet grass" and bought some home. He planted it in a pot and in the morning there was only 1 cm above ground level left even though he had hidden it till it grew a bit more prolific. Not sure how different it is from normal grass but they are crazy for it?