Thanks for your kind words and for requesting me again although I'm sorry that I was off my computer when you did so.
This type of situation is always especially frustrating for both owner, patient and vet alike. Typically when a dog's stools are completely formed and normal and yet return to a looser state after dog food (of any kind) is reintroduced, then I tend to think that the patient has a food allergy to somei ngredient in the dog food which is being fed.
I typically suggest that the owner take the label of the current dog food and purchase something completely different...both protein and carbohydrate ...or even grain free. I tell owners to avoid the same species such as turkey or duck if the current food contains chicken but rather select something with hooves or scales.
This can often be quite frustrating since it is usually a trial and error process and usually takes time to transition from the bland diet to various new foods being tried.
I'm having a difficult time explaining a food allergy given this pattern his stool consistency but I still believe that a complete change in diet may be warranted. Yes, ID is a very bland diet but perhaps the grain component of the food is more than he can tolerate when he eats it as the sole food.
I also worm these patients to eliminate internal parasites as a complicating factor even if stool samples have been negative. I worm with both Fenbendazole (Panacur) and Metronidazole together for 5-6 days to rule out giardia, hookworks, whipworms and roundworms.
I also have my patients on a probiotic which I believe I mentioned to you before.
I seem to recall that you said Zeus has always had a sensitive stomach. I often believe that these dogs are afflicted with Inflammatory Bowel Disease which has a strong dietary component triggering inflammation in the intestines. Often these patients need drugs such as Metronidazole to help calm things down so the advantage of this drug in combination with Fendendazole is that it does double duty, so to speak.
If my patient isn't behaving as expected (the stools remain loose), then I recommend blood work to rule out a systemic disease with possibly a gastrointestinal panel to evaluate B-12 and folate levels as well as possible problems with the pancreas. Even without running blood work, I'll often give my patients a B-12 injection since it won't be harmful and many dogs with gi issues are deficient in this vitamin. By the way, oral supplementation is not as effective as injections.
The fact that he's not otherwise acting ill is obviously a very good thing but I can understand that you'd like his stools to return to a normal consistency. I hope this helps you achieve that goal.