One suggestion - probiotics! I've never used them, but lots of people swear by them for keeping the gut healthy, especially with IBD dogs.
You can use people ones, but b-naturals might be a good source, & the woman who sells the stuff is a PhD nutritionist & did her dissertation (or something) on canine nutrition, She also is a Rottweiler person & will answer questions, she is very nice. There's also some good articles & info on her site.
http://b-naturals.com/default.php
Breezy....!:D