Healthy Guts Make Healthy Cattle by: Addie Womack SDSU Extension Livestock Production and Stewardship Field Specialist


Feed additives are added to beef cattle diets with goals such as improving health and performance or reducing antibiotic use and greenhouse gas emissions. There are medicated feed additives, including antimicrobials, anti-coccidials, and antiparasitics, with many requiring a Veterinary Feed Directive (abbreviated as VFD) for use. There are also nonmedicated feed additives, including probiotics, prebiotics, and postbiotics. Probiotics and prebiotics are used to improve the animal’s gut health, via the microbes. Postbiotics can often have health benefits for the host animal, such as beneficial impacts on immunity.


Prebiotics are food ingredients added to cattle diets to stimulate the growth and activity of microbes. Prebiotics are not digested in the stomach, but rather fermented in the large intestine. Commonly used as a prebiotic, oligosaccharides provide “food” for the favorable bacteria to grow within the gut. Prebiotics must also benefit the host animal’s health, often improving immunity.

Prebiotic Selection Criteria*

  • Resistance to digestion in the upper sections of the alimentary tract.
  • Fermentation by the intestinal bicrobiota.
  • Beneficial effect on host(s) health.
  • Selective stimulation of growth probiotics.
  • Stability in various food/feed processing conditions.

*Adapted from Markowiak & Śliżewska, 2018.


Probiotics have been defined as “live microbial feed supplements which beneficially affect the host animal by improving its microbial balance.” Cattle GI tracts naturally contain microbes, which aid in the breakdown of feed; when probiotics are used as a feed additive, they can alter this microbial population. This is of benefit to the producer and the animal by improving feed efficiency, feed digestibility, and the fermentation process. Probiotics have been shown to change fermentation end products, resulting in reduced methane production. Probiotics, since they are living, must be able to replicate after passing through the abomasum of the animal but also must remain stable during the feed processing.


Postbiotics are metabolic byproducts of microbes that result in health benefits to the host animal. Postbiotics have been shown to have anti-inflammatory properties and improve immunity of the animal. When added to the feed, they can potentially enhance nutrient absorption by the animal by promoting certain enzymes involved in digestion. Postbiotics are less susceptible to environmental conditions than probiotics, therefore processing and transportation pose less of a threat to the quality of the additive. So, while postbiotics may be mass-produced easier, they are fairly new to ruminant nutrition.


Pre-, pro-, and postbiotics can be used individually as feed additives for beef cattle, or a mixture incorporating all three can be formulated.

Think about it like this, prebiotics are used to feed the already present microbes, probiotics are used to ensure the right microbes are present, and postbiotics are a byproduct of the microbes benefiting the health of the animal.

The ultimate goal of these additives is to benefit the host animal in such a way that antibiotic use can be reduced. To achieve this goal, researchers are continually looking into the use of and benefits from these additives.


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