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.

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.

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.

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.

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.

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

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

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.

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

Read also What happens when horse feed contains yeast?