3 good reasons why Regulator Complete does not contain yeast

At Regulator Complete we work for calm, balance and durability in the horse's body.

That is why we have chosen not to add yeast to our feed.
Here are three of the most important reasons – all backed by research.

1. Yeast doesn't work the same every time

When reviewing the research on yeast in horse feed, one pattern is clear: the results are very inconsistent .

• Some studies find improved digestibility of fiber or increased energy utilization (Agazzi et al., 2011; Garber et al., 2020).
• Other studies find no effect under almost the same conditions (Grimm et al., 2016; Mackenthun et al., 2013).
• The effect depends on the type of feed, yeast strain, dose and individual differences in the horse.

👉 At Regulator Complete , we believe that feeding should be stable and predictable – every single day. That's why we choose ingredients with well-documented and consistent effects: fiber, protein and omega-3.

2. Lack of documentation for healthy horses

 Most positive results with yeast come from experiments on stressed or sick animals :

• Calves during weaning or antibiotic treatment (Liu et al., 2024).
• Slaughter animals where the goal is rapid weight gain (Yi et al., 2025; Pang et al., 2022).
• Horses on extremely starch-rich diets (Medina et al., 2002).

When looking at healthy horses fed a good roughage diet, there is very little evidence that yeast makes a real difference. Several studies directly show that the effect is minimal or non-existent (Grimm et al., 2016; Mackenthun et al., 2013).

👉 At Regulator Complete , we develop feed for horses in everyday life – not just for extreme experimental conditions. That's why we only use raw materials that have a clearly documented value for healthy horses. 

3. Yeast can overactivate the immune system

A well-documented effect of yeast is that it can stimulate the immune system through its content of β-glucans (Perricone et al., 2022).

• In the short term it can be useful, for example after illness.
• But with daily feeding, the immune system can work overtime.

The consequences can be:

• Energy loss because immune reactions use resources that could otherwise go to muscles and recovery.
• Low-grade inflammation, which affects mucous membranes, joints and muscles (Lucassen et al., 2022; Liu et al., 2024).
• More minor problems like soreness, slow recovery and more frequent vet visits.

👉 At Regulator Complete , we believe that riding and sport horses need calm and balance in their bodies – not an immune system that is constantly on alert. That is why we opt out of yeast.

Sources

• Agazzi A. et al. (2011). Evaluation of live yeast supplementation on digestibility in horses . J. Equine Vet. Sci.
• Garber A. et al. (2020). Effects of yeast on nutrient digestibility in horses fed high-concentrate vs. high-forage diets . Animals .
• Grimm P. et al. (2016). Influence of live yeast on nutrient digestibility in horses . Livest. Sci.
• Mackenthun E. et al. (2013). Effects of yeast culture on digestibility in horses fed hay-based diets . J. Anim. Physiol. Animation Nutr.
• Liu X. et al. (2024). Yeast peptides in calves: immune and anti-inflammatory effects . Front. Know. Sci.
• Yi S. et al. (2025). Effects of Yeast Cultures on Growth Performance, Fiber Digestibility, Health of Beef Cattle . Animals .
• Pang Y. et al. (2022). Yeast Probiotic and Yeast Products in Enhancing Livestock . J. Fungi .
• Medina B. et al. (2002). Effect of live yeast culture on ruminal pH and fermentation in horses fed high-starch diets . J. Anim. Sci.
• Perricone V. et al. (2022). The Role of Yeast Saccharomyces cerevisiae in Supporting Gut Health in Horses: An Updated Review… Animals . PMC9774806
• Lucassen A. et al. (2022). Saccharomyces cerevisiae fermentation product and the equine gut microbiome . Animals .