You might ask your vet about using this pro-biotic product. I am using it while some of my foster cats are taking antibiotics. Having said that, one of my kittens seems to have developed worse diarrhea (similar to what you describe) since I began to put it on their food. But the reviews from others about this product are good.http://www.amazon.com/FortiFlora-Fel.../dp/B000O5HXJ2
Other than that, I also had a cat with IBD many years back. I sympathize with you. Mine also did not respond to Prednisone.
I was able to get her stabilized on a canned wet food that is no longer made (Waltham's I think lamb and rice). But the lamb and rice combo seemed to really help her. It was a major crisis however, when Waltham altered the formula, so if possible see if you can get your cat stabilized on more than one brand of food. I realize this is close to impossible having been through it with my cat, but I feel like I have to say it
I found a really good site with links about IBD. You may already know about these. Here are the links. They include treatment discussions and support forums for cat IBD parents:http://www.marvistavet.com/html/body...l_disease.htmlhttp://www.maxshouse.com/inflammatory_bowel_disease.htmhttp://pets.groups.yahoo.com/group/F...yguid=32261064http://www.belfield.com/article1.htmlhttp://www.vet.cornell.edu/fhc/brochures/ibd.html
Good luck. My heart goes out to you and your kitty.