Read this:
Things improved a bit when the manufacturers removed all dairy from the pet foods. In the following years, the milk coated puppy and kitten chows went the way of the buffalo and some amazing things happened. Suddenly, there was a noticeable drop (to me, anyway) in the incidence of rheumatoid arthritis, asthma, and diabetes in the dog. I have not had a case of rheumatoid arthritis in forever.
from
http://dogtorj.tripod.com
His website is a little tough to read but definitely worth the effort. His finding makes a lot of sense to me and his approach in diet is eye opening.
I hope you read it. I believe taking his advise has helped my Jewel tremendously with her GME.