Bacteria must be live
A probiotic organism has to be alive to work in the gut. The reason for taking probiotics is to add “good” bacteria or yeast to the gut and have them outcompete some of the bad bacteria. For this reason the organisms need to be alive.
In a survey of dog foods that claimed to have probiotics, it was found that majority had no live bacteria in them. So feeding probiotic dig food to your dog is probably not worthwhile, unless you know that the food has organisms that are alive.
Bactaquin contains 1 billion (1,000,000) CFU* of Enterococcus faecium, this is 10 times more than Fortiflora.
Bactaquin also contains yeast extract (which is high in B vitamins) and fructooligosaccharide (FOS, a product of inulin and is a prebiotic, so it also helps stimulate bacterial growth).