OK, it sounds like you’re saying that your dog tested negative for EPI, which was my first concern. If he’s gaining weight and growing normally otherwise, I’d lean toward a food intolerance. Digestive enzymes and probiotics still might prove beneficial. Plain, canned pumpkin helps, too; but you need to remove the food first. Be sure you aren’t overfeeding (that’s a very common cause of loose stool). You can also fast him for a bit, which helps to rest the gut.
I’d switch him to a food with a different, single, protein and starch source. Keep track of every food you feed him and make notes about his reactions to them. This is how I narrowed down my dog’s sensitivities. Also keep in mind that sensitivities can be to a lot of different ingredients. My boy can’t have any fish or fish oil, garlic, chickpeas, lentils, garlic, barley, millet or flax. He tends to have a sensitive digestive system and does better with lower fiber foods and does well on Nature’s Variety Instinct Limited Ingredient Diet. That might be a good place to start.
I can tell you what I’ve found that works for me if you’d like, but if your dog is intolerant of an ingredient in one of those foods, they’re obviously not an option for you. I’d pick a very limited ingredient food and start with that. Merrick, California Natural, Natural Balance and Wellness Simple are a few other brands you might want to check out.
