Lactobacillus reuteri is a lactic acid bacterium found in a variety of natural environments, including the gastrointestinal tract of many animal species. It does not appear to be pathogenic and has health benefits. As part of the Lactobacillus family, L. reuteri has many of the same broad ranging probiotic health benefits. In dogs, researchers have found that L. reuteri may be the most resistant probiotic and may especially be helpful in controlling canine intestinal infections.

Lactobacillus Reuteri inhibits the growth of some harmful Gram-negative and Gram-positive bacteria, along with yeasts, fungi, and protozoa. Researchers found that Lactobacillus Reuteri can secrete sufficient amounts of reuterin to achieve the desired antimicrobial effects. Furthermore, since about four to five times the amount of reuterin is needed to kill “good” gut bacteria (i.e. L. reuteri and other Lactobacillus species) as “bad”, this would allow Lactobacillus Reuteri to remove gut invaders without harming other gut microbiota.

Supplementing the diets of young animals with Lactobacillus Reuteri helps them to largely overcome the stresses imposed by unhealthy environments. Lactobacillus Reuteri serves to protect against illness caused by S. typhimurium and other pathogens, which are much more common in crowded commercial farms. However, other studies found that it can help when the growth depression is caused entirely by a lack of dietary protein, and not by contagious disease. This raises the possibility that Lactobacillus Reuteri improves the intestines’ ability to absorb and process nutrients.