Hi Patricia,
I second C4C’s recommendation for a fecal test. I also second her recommendation for NutriSource, which is generally well tolerated by sensitive stomachs.
I looked at the NutriSource Large Breed Puppy (grain-inclusive formula) and it has 4% fiber. I also looked at the three foods you specifically mentioned and with the exception of the Royal Canin (of which, I’m not a fan), the others are pretty high in fiber. How is he doing on the Eukanuba? Any loose stool while eating that? Right now, whatever he’ll eat and does well on is what he should be eating. Prolonged loose stool can actually do more damage. His digestive tract is healing when he’s not having the loose stool, even if that means temporarily using the I/D – at least the Calcium is OK for a LBP in the I/D.
I’ve been through this with my Golden when he was a pup and finally have a good handle on things. What I would do is sit down and look at all of the foods you’ve fed him. See if there’s anything in common in those foods that he doesn’t do well on and those he does. Compare ingredients and nutrient profiles. Sometimes it’s a fiber issue, sometimes it’s an ingredient issue, sometimes it’s a protein issue.
