Probiotics are by definition living or viable bacteria that have a stabilising effect on the intestinal flora and thus influence the health of the host. They must not be pathogenic and must be acid-resistant. Usually, these are lactic acid producers(Lactobacillus, Bifidobacterium, Enterococcus).
There are numerous studies on their effects on the intestinal flora of dogs, meanwhile also some on the clinical effect. The use should be weighed up in each individual case and discussed with the family veterinarian. We will also be happy to advise you.
Probiotics for dogs are useful when used correctly. You will find a selection of products for dogs and cats that have been investigated in studies behind this link: Probiotics for dogs