We love Blue Buffalo pet food, which we attribute to our eldest kitty's incredible decrease of dependence on insulin. She has, unfortunately, had very fluid bowel movements over the last couple months (nearly since we started using BB). We thought it was her change in insulin, as she swapped to the new brand about the same time, but Zeus started having identical liquid poo the day after he started on BB. Some quick research online, not certain if it was his food, stress, or change that caused this, we found that some dogs and cats have responded to the dry BB foods with very loose stools. Reading several reviews and hitting a few discussion groups, we found out that some people solved the issue by mixing the dry & wet BB foods at meals.
We tried, and his stools have progressively returned through each session to solid... not hard, but well formed. I NEVER thought I would be evaluating puppy and be happy to find soft-yet-solid feces. As this appears to have worked for the puppy, we are following up with Ophelia by feeding her more of the wet food through the day... the initial results seem positive.