congratulations on your decision - dobies are great! haha not as good as rotties - but we won't discuss that!
My vet put Roodie on "Professional" brand dog food - Roodie was way overweight when we first got her - (at the spca) and she had so many health problems - it took about 4 weeks and her skin is now perfect and all problems seem to have disappeared - it's not too expensive either -