diarrhea and dog foods

Question
My lab/pit mix (19 months old) has had problems with diarrhea--sometimes explosive--for about a month and a half. However, when I put her on rice and chicken, the diarrhea clears up. I've had her at the vet several times. They have given her a few rounds of metronidazole (up to 1000mgs per day, the max for her weight), and given her a shot of penicillin. But nothing seems to help. The fecal float showed nothing so the vet said she needs to be on Royal Canin prescription venison and potato food (she had been on Iams large breed). It would cost me about $70 a month and I can't afford that. A friend suggested trying PetSmart for cheaper alternatives. I now have her on Nature's Recipe venison and rice and it seems a little better (no explosive diarrhea) but her stools are still very runny. She's been on it for not quite a week and I also started her on a probiotic supplement. What else can I do? I don't want to have to put this dog down. She's a great dog! Excellent with the kids, but I just can't afford to keep taking her to vet. Please help!

Answer
Hi, Laura,

I understand your concern about the expense of the Royal Canin - one of my dogs is on the Duck and Potato for food-allergy-related seizures.

You mention that when you put her on rice and chicken, the diarrhea cleared up.  Are you meaning a rice and chicken dog food, or you were cooking rice and chicken for her?  If it was a purchased food, would it be worth going back on that?

I don't know if the digestive systems of dogs operate similar to that of humans, but I just learned recently that the purpose of the human colon is to remove liquid from the digested matter and send it to the kidneys.  When the colon is not working properly or is irritated, it doesn't do its job and all the liquid comes out as diarrhea.  So, I'm guessing something is going on with her lower bowel.  

As far as home remedies, you can try adding canned pumpkin to her food - this is NOT pre-made pie filling, but the actual canned cooked pumpkin from which one would make their own homemade pumpkin pie.  The grocer will know if you ask.  This seems to help bind up a dog's stool.  

Adding fiber in the form of something like Metamucil may also help.

You can also try Imodium; this is safe to use on dogs; give the child's weight dose.

It is also possible for dogs to have irritable bowel syndrome, like humans.
Here is a link to information on IBS:
http://www.irritablebowel.org/syndrome-dogs.html