Therapeutic Probiotics:
If your dog has recently been on antibiotics which destroys the good bacteria along with the bad (stress can also contribute to this) - then you need to provide probiotics/good Bacteria in amounts that can recolonize the gut which is in the millions. Live yogurt / kefir does not have enough bacteria to do this- you need a product that can provide these amounts like Benebac or B Naturals Probiotics. These are also formulated specially for dogs with a more species appropriate bacteria - Enterococcus faecium. Provide this supplement a few hours before or after antibiotics and continue for a few weeks after the drug therapy has ended.
Dietary Probiotics
Live yogurt and kefir are probiotics you can add as a daily part of your dog's diet as a general supplement. Kefir has a broader range of bacteria and the lactose is more predigested so it is recommended as dogs can have lactose intolerances.
General Strategy
Although there is an increasing amount of research regarding probiotics for canines, there's no exact science, as with most nutrition issues, that feeding x amount of a specific range of bacteria will successfully populate the gut with the right kind of flora or healthy bacteria which is what probiotics are supposed to do. One reason is we don't know if they all survive the acidic environment of the stomach, or which specific bacteria strains are capable of doing this. There are people who think that you can't process and bottle live bacteria- and there are some who think there isn't enough of a range of bacteria in naturally occuring foods like kefir. So its generally reccomended that you provide a broad range of these bacteria by feeding a range of kefir, green tripe, yogurt and a probiotic product and at different times- its thought that feeding probiotics between meals helps avoid the acidic environment.
The ABC's of probiotics Narda Robinson DVM
The difference between probiotics and digestive enzymes. Lew Olsen Ph.D
Probiotics and Diarrhea
Some studies showing benefits of probiotics for diarrhea:
Clinical benefits of probiotic canine-derived Bifidobacterium animalis strain AHC7 in dogs with acute idiopathic diarrhea.
Effects of a probiotic intervention in acute canine gastroenteritis--a controlled clinical trial.