I have not heard back from you but do want to leave my thoughts for your return.
Now based on the signs we are seeing, we do have a few concerns. Common causes we need to consider include bacterial or viral gastroenteritis, parasites, protozoa infections, general dietary indiscretions, and ingestion of harmful items (ie toxins, plants, non-edible items).
With this all in mind, you were right to start a light diet here. This should get more nutrients in and result in less diarrhea to pass. Of course, do make sure to feed this as small frequent meals to help reduce the gut's work load. As long as improvement is being seen, I usually advise continuing this until the signs are settled, and then weaning him slowly back to his normal diet.
Next, if he has not been wormed recently, do make sure to cover that base. Worms and protozoa both can cause diarrhea in the young dog. Ideally, we'd want to use Panacur (OTC at your vets and most pet stores) since this also can clear some of our protozoal concerns as well as worms. Of course, make sure to have an idea of his weight (most vet practices will let you use their scale as part of buying wormers) to ensure you get the right dose.
Furthermore, since he is young, we have to monitor his hydration here. To check this and ensure he’s not becoming dehydrated from lost fluid in this stool, there are a few things you can test. Further to checking for gum moisture, you will want to make sure his eyes are not looking sunken and that he doesn’t have a "skin tent" when you lift the skin. To see how to check these parameters for dehydration, you can find a good video HERE (http://www.ehow.com/video_12232503_dog-dehydrated.html). If you are seeing any signs of dehydration already, then that would be our cue to have him seen before this becomes an additional issue for him (especially as it is often dehydration that makes them feel unwell).
Finally, as long as there is no blood in those stools, you can consider trying a pet safe anti-diarrheal. As I am sure you appreciate, these would not be a cure for infectious issues; but it can still be of benefit. It will reduce diarrhea load, allow the body to absorb more water/nutrients, and soothe the upset gut. In regards ***** ***** options, the one we most commonly use is Kaolin/Kaopectate (More Info/Dose @ http://www.petplace.com/article/drug-library/library/over-the-counter/kaolin-and-pectin-kapectolin-k-p)). This is available OTC at most pharmacies. Alternatively and ideal here with those farts (a sign that his good gut bacterial population is imbalanced), you could use Propectalin, Canikur, Fast Balance, and Protexin Pro-Fiber (all OTC at vets, pet stores, and even Amazon). All will slow diarrhea and those last ones have the added bonus of providing support to the delicate good GI bacteria. So, these can be used as a short-term means of soothing his upset GI and addressing the gas at the same time.
Overall, there are a wide range of agents could trigger this GI upset we are seeing. Therefore, we’d want to start supportive care to try to settle this. If he appears dehydrated already or doesn’t respond to the above within 12-24 hours (since he is young); then we'd want to get his vet involved. They can assess his hydration, rule out fever, and test a stool sample to pinpoint which agent is lurking here. Depending on their findings, his vet can treat him with antibiotics +/- anti-protozoal treatment to settle his gut and get him back to passing normal.
All the best,
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