Equine knowledge:

yeast is not equal to brewers’ yeast!

Yeasts, live yeasts, double fermented or cultured yeasts, and real brewers’ yeasts. Probiotics, prebiotics, and postbiotics – sounds good, but what exactly is it and is it also suitable for horse feeding?
All about horse feeding.


Pro or Pre or what? A small difference with a big effect!

We bring light into the darkness and the facts on the table! The use of brewers’ yeast from breweries was common in the past, but today it is rather an exception. Yeasts differ in terms of origin, content, activity, and their mode of action. Basically, a true brewery brewers’ yeast is always inactive, thus a so-called inactive yeast. Brewers’ yeasts can therefore never be probiotics (live yeasts), they always act post- and prebiotically.

Brewers’ yeast for a balanced intestinal flora

The non-digestible fibres promote the growth and activity of intestinal bacteria – perfect for a gut in balance. The most important facts at a glance:


  • Indigestible carbohydrates
  • Inactive, non-reproductive
  • For example, brewers’ yeast (Saccharomyces cerevisiae) and its components such as mannanoligosaccharides (MOS) and glucans from the cell wall
  • Prebiotics cannot be digested by the body's own enzymes in the stomach and small intestine and get into the large intestine.
  • Microorganisms use them as food and form SCFA (short-chain fatty acids) such as propionate or butyrate, which serve as an energy supply and promote intestinal health.
  • Prebiotics balance the intestinal flora by stimulating the proliferation of beneficial bacteria and displacing potential pathogenic germs.

How can I tell if it is a prebiotic (e.g. brewers’ yeast)?  

  • Brewers’ yeasts can be identified on the label.
  • They are to be declared within the heading COMPOSITION, as individual or supplementary feed.
  • Example brewers’ yeast as an individual feedstuff composition: 100% brewers’ yeast or Saccharomyces cerevisiae
  • Example Leiber YeaFi® BT as supplementary feed: individual ingredients are to be declared in descending order. Composition: spent grains, brewers yeast.

Live yeast, unfortunately not undisputable

The live yeast should theoretically support digestion. However, the study base – especially in the equine field – is so thin that the effectiveness of probiotics has not been sufficiently proven. Here you will find more information:


  • Active or living organisms capable of reproduction
  • For example, yeasts of the genus Saccharomyces cerviseae (known as live yeasts)

Application and effect

  • Approval as intestinal flora stabiliser or digestibility enhancer

Probiotics in horse feeding

  • There are only very few impact studies.
  • Many studies could not prove positive effects.
  • Effectiveness is controversial.

How can I tell if it is probiotics (live yeast)?

  • Live yeasts can be identified on the label.
  • They must be identified as zootechnical additives including EU registration number, strain, and indication of CFU (colony forming units).
  • Example: zootechnical additives: Saccharomyces cerevisiae CBS 493.94 (4a 1704) 20.0*1QA9 CFU

New little helpers?

They belong to the family of biotics and are relatively new on the market. The research situation is correspondingly thin. We have compiled the few facts together.


  • Postbiotics is a new definition coined in 2021 by ISAPP (International Scientific Association for Probiotics and Prebiotics).
  • Currently, the term postbiotic is used very often, however, official bodies such as EFSA (European Food Safety Authority) have not yet authorized the definition of postbiotic! They distinguish scientifically correct only between prebiotics (inactive) and probiotics (active).
  • According to the ISAPP, a postbiotic is inactive microbial cells and/or metabolites (metabolic products) and/or cellular components that have a health-promoting effect.
  • According to this very broad definition, all prebiotics (such as brewers’ yeast) and inactivated probiotics would, at the same time, also be postbiotics – quite confusing!

Real brewers’ yeast, real effect.

Here, you have it in written form!

Brewers’ yeast is a well-tried feedstuff with a long tradition in horse feeding. Its use is proven in practice and is often recommended in the scientific literature, for example:

  • in case of chronic intestinal inertia or resected bowel sections
    (COENEN & VERVUERT 2020)
  • or horses prone to colic or diarrhea
    (ZENTEK et al. 2008, COENEN & VERVUERT 2020)
  • in the case of prolonged digestive disorders, damage to the intestinal flora, loss of appetite, or general weakness in performance
    (COENEN & VERVUERT 2020)
  • in the case of pre-reporting myopathies due to strain or diseases of the liver
    (COENEN & VERVUERT 2020)
  • as protein feed especially in the breeding and rearing
    (KARP 2011)
  • for rations rich in concentrated feed and low in structure
    (COENEN & VERVUERT 2020)
  • for rations with low hay qualities
    (MORGAN et al. 2007)

Various yeasts

on the market

(production process)


(production process)

  • baker’s yeast


  • live yeast (probiotics)

(production process)

  • ethanol yeast or molasses yeast


  • inactive yeasts (prebiotics)

(production process)

  • bioethanol or sugar yeast


  • inactive yeasts enriched with minerals (e.g. selenium yeasts)

(production process)


(production process)

  • fermentation yeasts or "yeast cultures"


  • cereals – nutrient substrates with inactive yeast contents

(production process)


(production process)

  • urea yeasts


  • yeasts enriched with urea to increase the protein content

(production process)

  • brewers’ yeast or "real brewers’ yeast"


  • inactive brewers’ yeast (prebiotics)

  • inactive brewers’ yeast – fibre products (brewers’ yeast and functional fibres)

Our horse products:

Your horse deserves the best feed.

100% Brewers’ Yeast
Real brewers’ yeast, really good effect for your horse!

At Leiber, brewers’ yeast is refined using state-of-the-art processes, some of which were developed in-house, and inactivated in the process. Leiber® Brewers’ Yeast is rich in many bioavailable active ingredients and nutrients such as proteins, amino acids, B vitamins, and trace elements. Leiber® Brewers’ Yeast is a "real" brewers’ yeast!

Recommended use
40% brewers’ yeast + 60% fibres
The successful formula for healthy horse nutrition!

LeiberYeaFi® is a unique synergy of inactive brewers’ yeast with high fibre and dietary valuable, functional fibres. Brewers’ yeast is rich in bioavailable active ingredients and nutrients such as proteins, amino acids, B vitamins, minerals, and trace elements.

Recommended use

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