A couple things you might try. Slippery Elms Bark.
http://www.felinecrf.org/holistic_treatments.htm#SEB1
http://www.littlebigcat.com/health/slippery-elm/
Another probiotic for animals...supposed to be tasteless:http://www.amazon.com/gp/product/B002WDGLL0/ref=oh_details_o03_s01_i00
Slippery elms was the only thing that worked on my dog when she had it. It can be used on cats as well as dogs. I used to make a gruel, heating it
into a gel like substance. Never tried just sprinkling it. It does suck up the water,so I think making the gel is better
To give internally, mix about 1/4 teaspoon of Slippery Elm bark powder with cold water for every 10 pounds of body weight. For very small dogs, it is fine to use the same 1/4 teaspoon dose. The bulk powder may be very fluffy, so pack it down as much as possible to measure it. Alternatively, use 1/2 capsule (per 10 pounds), opened and the contents mixed with water. Slippery Elm powder will absorb many times its own weight in water, so be sure to add enough to make a moderately thick gruel. This gruel can be given before meals by syringe or eyedropper, or added to baby food, canned food, or a homemade diet. It has a slightly sweet taste and is usually well-tolerated by cats and dogs when mixed with food. Give a dose 5 minutes before meals for sore throat, and before or with meals for digestive tract problems, such as inflammatory bowel disease, until symptoms resolve.
Another probiotic for animals...supposed to be tasteless:http://www.amazon.com/gp/product/B002WDGLL0/ref=oh_details_o03_s01_i00