Not sure on the food type.
One thing I find for many dogs, mainly ones such as rotti, pitbull or shepherd is RAW MEAT. Our pet food store has it and so does your grocery store! Even asking people for freezer burned meat they do not want. This helps keep the fur, skin, muscles and bones/joints healthy. It definitely works better than just commercial food for highly active dogs.
Before my pup Scottie passed away he was losing weight.. So we got raw meat into the diet to have him gain weight.
Breed for the breed, not for the money; the words any REAL breeder would understand.
You must know nothing in order to know all, for all is nothing and nothing is for all.