I too think probiotics and enzymes can do wonders sometimes! When the small intestine becomes unbalanced and the flora gets funky, it can cause all kinds of problems. They can really be essential for post-giardia puppies, since giardia actually begins to digest the GI tissue in puppies (not seen as much in adults).
I like this brand, which is formulated for dogs and provides both the enzymes and probio in one product (you put a pinch on their food):
Nature's Farmacy - Store - Product Details