Yeast in horse feed – when does it make sense?

Should your horse have yeast in their feed?

At Regulator Complete , we have chosen not to add yeast – and there are good reasons for that.
Yeast (e.g. brewer's yeast and yeast extracts) can affect digestion, immune function and energy utilization. For some horses this can be an advantage – but for many it is not necessary at all, and in some cases it can be a disadvantage.

We want calm, stability and natural balance in the body – not unnecessary stimulation.

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What is yeast and why is it used for horses?

• Feed yeast of the type Saccharomyces cerevisiae is often used in mash, supplements and feed mixtures.

• Yeast contains, among other things:

  • β-glucans (25–35% of dry matter)

  • Mannan oligosaccharides (MOS) (20–25%)

  • Proteins, vitamins and other cell components

• β-glucans from yeast are known to affect both the immune system and intestinal flora.

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1. Yeast can stimulate the immune system

• How it works: β-glucans activate immune cells (macrophages) in the gut. Macrophages are among the first to take action when the body detects something foreign.

• But – an immune system must be ready , not on alert all the time .

If the immune system is overactive, it can cause:

• Increased energy consumption → Immune reaction requires energy and can affect metabolism – especially in frugal horses.

• Inflammation and tissue damage → Prolonged activation can damage mucous membranes and joints.

• Dysbiosis and “leaky gut” → The balance of the intestinal flora can be disrupted and the protective barrier of the intestine can be weakened.

• Altered behavior and stress response → Overstimulation can affect appetite, sleep and behavior.

✅ Practical conclusion: If your horse is healthy, gets good roughage and the necessary vitamins and minerals, additional yeast is rarely needed.

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2. Yeast can increase energy absorption

• Yeast can improve the utilization of fiber in the hindgut by 3–10% .

• This means that the horse gets more energy from the same feed – good for horses that need to gain weight, but unfortunate for horses with low energy needs.

• Many experiments with yeast have been conducted on slaughter animals, where rapid weight gain is desired.

For horses that need to lose weight, you want:

• High fiber content, but low energy intake

• Long chewing time and fullness – without too many calories

• Here yeast can be a disadvantage.

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How much β-glucan does yeast contain?

➡️ Yeast contains 10–20 times more β-glucan than regular fiber raw materials - it makes a clear difference.

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When can yeast make sense?

• If the horse is sick, stressed or undergoing rehabilitation

• If the roughage is of poor quality

• After antibiotic treatment, for example, to support the intestines

When is yeast not necessary?

• If the horse is not going to put on

• If you want low energy intake per kg of feed

• If intestinal function is already good and roughage is okay

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Our choice at Regulator Complete

We do not use any yeast products or yeast extracts in either the mash or vitamin-mineral mixtures.

Instead, we work with:

• Natural raw materials such as flaxseed, soy hulls, beet pellets and green pellets

• Balanced fiber profile with pectin and β-glucans in moderate, natural amounts

• Calm digestion , so the products are suitable for both sensitive stomachs and horses with low calorie requirements

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Conclusion

• Yeast is not dangerous – but it is not necessary for all horses either.

• For frugal horses or horses in good health, yeast can in some cases do more harm than good.

• At Regulator Complete, we choose calm, stability and natural balance – without yeast .

📧 Are you unsure about what suits your horse best? We are happy to help you find the right solution.
If you would like a consultation, click here.

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Want to know more about the research behind yeast and horses?

Read also What happens when horse feed contains yeast?

Ofte stillede spørgsmål om gær i hestefoder

Er gær farligt for heste?

Nej. Gær er ikke farligt. Spørgsmålet er, om din hest har brug for det. For en sund hest på godt grovfoder er svaret som regel nej.

Er gær en god idé til en hest, der skal tage på?

Gær kan øge energiudnyttelsen af det samme foder. Men effekten er uensartet mellem studier, og der er mere sikre veje til flere kalorier, blandt andet olie og fiberrige produkter med højt energiindhold.

Hvordan ser man, om et hestefoder indeholder gær?

Kig efter de latinske navne i listen ovenfor. Står der intet af det, indeholder foderet ikke gær.

Skal hesten have gær efter en antibiotikakur, hvis dyrlægen anbefaler det?

Nej. Følg dyrlægens anvisning. En kort periode efter sygdom eller antibiotika er netop den situation, hvor gær kan give mening.