Probiotics and Yeast Culture Products and Their Use in Horses
  by Robert N. Oglesby DVM

Probiotics have been described as a live microbial feed supplement which beneficially affects the host animal by improving its intestinal microbial balance and exert health effects beyond inherent basic nutrition. The earliest published report of this concept was by Elie Metchnikoff in 1907 who conjectured that ingesting fermented milk products were responsible for longevity of certain ethnic groups by improving the quality of the intestinal microflora. The term was coined in the 60's.

A related product but not truly a probiotic are killed Saccharomyces culture and byproduct nutritional supplements. These have come to be termed prebiotics. Saccharomyces is baker's yeast and many of the organisms are yeasts used in fermentation processes. Though often packaged live the survivability of these products is very short and therefore should be thought of as a nutritional supplement. However we will discuss them here do to their similarity to probiotics.

There is a growing body that certain live cultures of particular yeast may be useful in the treatment of colitis in horses. There has been an explosion of pre and probiotic products available and a concomitant rise in the use of these products. This article describes the principles of probiotic therapy, the research available into efficacy, and which products have solid research behind their use.