You first need to determine the cause for the diarrhea. If your dog has not seen the vet recently for a fecal exam, I would do this first to rule out parasites as the cause. This is different from a blood test.
Dogs can also have diarrhea because of intestinal obstructions or other causes. If you know that he swallowed a rawhide or other object (is he a chewer), you need to see the vet as soon as you can. Obstructions cannot be treated at home and most dogs cannot pass them on their own. This can be confirmed with an x-ray.
Sometimes, this is caused by a simple parasite problem or coccidia or giardia. You can find out with a simple fecal exam.
Dogs usually do well a bland diet of only boiled hamburger and white rice (never tried bison, myself!) and it helps to settle the stomach. Be sure and keep this up until you can get to the vet.
If you supect that he is dehydrated, you can give him pedialyte or gatorade instead of water to increase his hydration.
Let me know if you still have questions.
