What are Probiotics, Prebiotics and Synbiotics and Why Should My Horse Care?

What are Probiotics, Prebiotics and Synbiotics and Why Should My Horse Care?

by Richard G. Godbee, Ph.D., PAS, Dipl. ACAS-Nutrition

With the amount of advertising on television touting the benefits of probiotics it is difficult to not at least have heard the term. Searching with the term “probiotics” on the internet returned 12 million hits in less than 0.2 seconds. Adding “for horses” to the search returned 439,000 hits. Basically there is a plethora of information on probiotics available to anyone wanting information. Part of the goal of this article is to provide a Cliff’s Notes version of what each term means and how they impact the overall health of our horses.

Animals and bacteria have had a love-hate relationship since the beginning of time. Bacteria were discovered in the 1600’s and in the 1800’s crude vaccines were being used in Europe. Early work on bacteria focused on the pathogenic or disease causing aspects. It was not until the 20th century that certain bacteria were recognized to have positive health benefits for humans and animals. The earliest work involving gut microbes and health was in a breast-fed infant. The term probiotic was first introduced in 1953. This definition was in contrast with antibiotic and suggested probiotics supplied factors that stimulated growth. Roy Fuller later defined a probiotic as “a live microbial feed supplement which beneficially affects the host animal by improving its intestinal microbial balance”. The definition is somewhat fluid as it changes as more information is obtained.  Lactic acid bacteria form the core of these probiotics. To be used in feed products they must be recognized by the FDA. They are currently classified as “GRAS”, generally recognized as safe. One important property is the bacteria must be viable, i.e. capable of colonizing the digestive tract. Certain yeast and fungi may also have probiotic properties.


  • Probiotic: live microorganisms which when administered in adequate amounts confer a health benefit on the host. Most of these are lactic acid
  • Prebiotic: a selectively fermented ingredient that allows specific changes, both in the composition and/or activity of the gastrointestinal microflora that confers benefits upon host well-being and health (food for probiotics that may also have a positive impact on gut and host health, usually indigestible fiber e.g. mannooligosaccharide).
  • Synbiotic: mixture of prebiotics and probiotics (the prebiotic is usually chosen to optimize the growth of desired bacteria, probiotic).
  • Yeast “culture”: generally from genus Saccharomyces and may be cerevisiae orboulardii
  • Colony Forming Units: CFU’s; number of viable bacterial cells per unit of measure, maybe given in thousands to billions

What can probiotics/prebiotics/synbiotics do for my horse?

  • Improve digestion of certain feedstuffs into absorbable
    • Improve the absorption of certain
    • Certain yeast strains have been shown to improve fiber
    • Produce short chain and volatile fatty acids from fiber that can be used as an energy substrate by the host animal. The majority of energy provided by forages is from short chain fatty acids produced in the large
  • Produce many of the B-vitamins required by the horse at least for
  • Improve the health of the
    • Alter the pH of the gut to decrease pathogenic bacterial
    • Stimulates the immune response and enhances innate
    • Increases the effectiveness of the tightness of the cells lining the intestinal walls.
    • Provide direct competition with pathogenic
  • Decrease inflammation by decreasing inflammatory cytokine
  • Secrete antiviral, antibacterial, and antifungal
  • Decrease loose manure.

What are some factors to consider when choosing a probiotic or synbiotic for my horse?

  • Look at the total number of CFU’s per dose. Generally the higher the concentration the greater the ability of the bacteria to positively affect the horse’s health. Most probiotics are susceptible to heat and cannot be put in a pelleted feed. There are some that can withstand the heat of pelleting, look at the CFU’s in the product; this can provide a measure of survival. The probiotic must also be able to survive the acid environment of the stomach and the digestive enzymes normally found in the stomach and small
  • In addition to the prebiotic, β-glucans may be added to the product. β-glucans are derived from the cell wall of certain yeast and plants and have been shown to increase the immune response by the
  • How often do I need to use the product? Horses under stress from training, traveling, showing, etc, may benefit from a daily synbiotic. Horses under less stressful activities may benefit from receiving the product every two or three times per week.
  • What should I expect to see when using a probiotic/synbiotic? Since most of the effects of the product occur in the digestive tract or “inside” the horse, visual changes are difficult to see. Obviously with horses having loose manure, cow pies, it will be easier to see changes.

Why do I want to feed a probiotic/synbiotic? Think of a quality effective product as a digestive insurance policy that help provide for the overall health of your horse.