Direct Fed Micro Organisms also known as Probiotics are actual living organisms that have a positive effect on the intestinal flora where many different bacteria reside. The gastro intestinal tract of your pet (people too, as both are mammals) contains over 400 species of micro organisms.
Pet food with probiotics is definitely a good choice when it comes to a holistic pet foods, these good guys block bad bacteria from setting up house in our bodies. Without good bacteria, bodies are less able to fight off disease, adequately absorb food and intestines become overrun with toxins and waste, which set the breeding ground for disease. 
Lactobacilli exist in an animals system naturally but are depleted by illness, stress, trauma or ingestion of antibiotics and antifungal medications administered to fight infections. Antibiotic and antifungal medications kill not only disease causing bacteria but also the beneficial lactobacilli present in your pet’s intestine. 

Plain yogurt that has low sugar content is also a rich source of this bacteria and a teaspoonful of yogurt added to your pet’s food is also a good way of naturally supplementing their diet.

Benefits of Probiotics

  • Improves digestive health
  • Helps prevent and treat diarrhea, digestive disorders, yeast infections and urinary tract infections
  • Boosts the immune system
  • Helps counteract the side effects of medications such as antibiotics and anti fungals
  • Aids problems associated with flatulence such as bad breath, gas and smelly feces
  • Improves the condition of the coat and prevents shedding 
  • Assists in relieving pain caused by arthritis
  • Helpful during times of stress including traveling, kenneling or training and after deworming.
  • Forms a natural protective barrier which keeps opportunistic pathogens (like Salmonella and Escherichia coli) from proliferating.
  • Provides easy-absorbable energy. 
Recommended for normalizing digestion, food intolerances, poor diet, supporting regularity and gastrointestinal, immunological and neurological support.
Many dog foods on the market fail to supply these helpful guys so it's important to read your labels closely to find out which dog foods contain probiotics. The best foods should include more than one of the following:
Probiotic Gate Keepers
Lactobacillus Acidophilus, Bacillus Subtilis, Lactobacillus Casei, Bifidobacterium Thermophilum, Lactobacillus Lactis, and Enterococcus Faecium. A good variety of direct fed microbials is a plus when determining a good pet food ingredient list.
When the large intestine is colonized by these so-called good bacteria, there is simply less room left  for bad types to flourish.