dog - diarrhea

Question
I have a dog I adopted from the pound, approx. 2 1/2 years old.  In the past 4 months he has had recurring problems with diarrhea, but I cannot tell what is causing it.  Would changing his food help?  I cannot find anything in the yard that he may be getting into that would make him sick.  My other dog is not having these problems.  They stay in the house during the day and outside for a few hours in the evenings, but I let them stay outside during the day on the weekends to play.  Could the heat be causing his illness?  I make sure they have fresh water. Thanks

Answer
You should take a stool specimen to the vet to check for intestinal parasites especially giardia.

You can try feeding Hill's Sensitive Stomach or one of the more natural foods that are limited ingredients such as Nature's Recipe Venison and Rice.

I would recommend adding digestive enzymes into his diet such as Prozyme as well as giving him probiotics like Acidophilus.