My Sheltie, Charlie, had many health issues. He had diarrhea since he was one and he eventually suffered from pancreatitis when he was around 8. I got help from Karen Murray who runs a blog, I don't remember the name of the blog but if you want I can go look for it. Anyway, she recommended options and I took her advice and the results were miraculous. I started him off with a pancreatin enzyme with every meal and slowly switched him to The Honest Kitchen. Because he had allergies we went with the Preference variety with raw meat added but they have other options now that are low-fat. Zeal and Verve are what I think they are called. After I switched he never had any other health issues. He was hypothyroid so he ate as much as a Great Dane so I stuck with the preference because it was cheaper. I spent around $100-150 with the Preference and the Zeal would have been around $300 a month for him. It was expensive but oh so worth it. It helped improve his quality of life so much.
Charlie: CGC - Sheltie 4/22/01
Harry: Sheltie 03/05/2013

RIP Wally: CGC, mdr1 neg., OFA - Sheltie 10/23/08-7/6/2012