Hi, everybody, I am new here and was reading all your posts.
Have you ever thought that you are comparing commercial dog food with commercial dog food. Instead of comparing commercial dog food and a natural diet? There is absolutely no comparison which is healthier and cheaper!
I own 4 Golden Retrievers, I used to breed them. I feed all of them a biologically appropriate diet. Called BARF. It is a lot cheaper! Twice! Once on your wallet by paying a fraction for dog food. Second by not having dogs sick. So I am saving on the vet bills too, well into old age.
Consider it, specially with big dogs like Rottweiler, just perfect.

I am a professional dog groomer, ex breeder, dog trainer, and teach people how to feed their dog correctly. The one thing that ALL the dog brands have in common is 3rd grade ingredients and they are all cooked. There is no anti-oxidants in them. The cooking processed makes food rancid for dogs. So you are actually slowly poisoning your dogs. As the cooking process kills most nutrients that dogs need and is only available from raw and fresh foods!
The Vets know about this too! But they stay silent, as they like to earn money of your sick pets! Plus the average Vet had about 4 hours of training in food! and that by Pal!
I live in Australia, so Im not advertising here, OK? But, I do have a website set up for my clients, to unravel the mystery of feeding your dog better. If you like have a look, maybe it will help you to feed your dogs healthier and cheaper. www.pet-affair.com.au
Got any more question write to me or buy the book "Give your dog a bone, by Ian Billinghurst, he will open your eyes to what is going on in the commercial dog food industry! All I can say, YUK!!