As we head into spring, we will undoubtedly be thinking of ways that we can manage the change in season and the spring grass flush that comes with it. The hindgut is a complex, important organ for all aspects of equine health and performance, so looking after it is vital.
The equine hindgut
Horses rely heavily on fermentation by several different species of bacteria to digest plant material in the large intestine.
The complex interactions that occur between the microorganisms in the hindgut microbiome mean that it is a very sensitive organ, and can be vulnerable during times of change. Pre and probiotics, whilst different compounds, work synergistically to help support the hindgut microbiome. Think of the probiotics as the workers, and the prebiotics as their meals. One could not exist without the other, and both play a vital role in promoting overall health by supporting normal function of the hindgut.
Disturbance of the microbiome can lead to common issues such as colic and metabolic syndromes, mostly as a result of an alteration of fermentation patterns. As a direct result, nutrient absorption is decreased, and overall health can be impacted.
Research into the equine hindgut is limited compared to that of the human, but what we do know, is that pre and probiotics can provide several benefits to the sensitive ecosystem. Many of us will choose to feed a gut balancer containing Saccharomyces cerevisiae to provide our horses with extra support – but how does this ingredient make a difference?
What is Saccharomyces cerevisiae?
Saccharomyces cerevisiae (S. cerevisiae) is a single-celled yeast species widely recognised in nutritional science for its role in fermentation and digestive support. Extensively studied across animal nutrition, selected strains are used in equine formulations for their stability, well-characterised biology, and functional activity within the gut environment.
These helpful microbes are known as probiotics, and they colonise the digestive tract and help to facilitate functions such as fermentation, digestion and nutrient absorption. Probiotics also aid immune function, by reducing the numbers of pathogenic bacteria through processes such as antimicrobial production.
Unlike bacterial microorganisms, S. cerevisiae is a beneficial yeast species with a robust and stable structure. Its cell wall contains biologically active compounds, including beta-glucans and mannan-oligosaccharides (MOS), which are prebiotics that have been studied for their interaction with the gut environment.
Why it is important for digestive health
Research suggests that S. cerevisiae may help to maintain a stable fermentation profile within the hindgut, supporting efficient fibre utilisation and microbial balance. This stability can improve the digestion of low-quality forages, increase nutrient digestibility and help to maintain caecal pH. These benefits mean that horses are better able to utilise the nutrients from their forage, thus having a direct impact on general health and energy production, as well as reducing the risk of colic and other hindgut disturbances.
Supplementing with live yeast can also provide the following benefits:
- Supporting microflora in the caecum
- Improved fibre digestion
- Limiting the overproduction of lactic acid in the caecum
- Improved body condition
What is encapsulated live yeast?
When feeding live yeast-based products to horses it is essential that they are provided in a form that protects them from stomach acid and ensures they reach the hindgut alive. Encapsulated live yeast is protected from acidity, heat and moisture by a layer of dead yeast cells, which enhances stability. This means it can move through the gastric stomach, and be broken down in the hindgut, where it can be best utilised by the body.
This unique protection system ensures that the optimum level of live yeast reaches the hindgut alive, without being affected by the conditions mentioned above. The benefits include stabilisation of the conditions in the large intestine resulting in the stimulation of natural fermentative activity, improved fibre digestion and nutrient absorption, and aids the efficiency of digestion.
Science Supplements Gut Balancer contains optimal levels of encapsulated S. cerevisiae, as well as a source of mannan-oligosaccharide (MOS), fructo-oligosaccharides (FOS) and beta-glucans, which help stimulate the growth of good bacteria and bind fungal mycotoxins. You can find out more about Gut Balancer here.
Knowing when to feed it
The role of the equine hindgut contributes significantly to overall health and nutrient digestion, so looking after this and providing support will always be beneficial. Many balancers and vitamin and mineral supplements now contain live yeast to provide general support, but some horses, or situations, may call for a little more, such as in the form of a specific gut balancer or support supplement.
Supplements containing S. cerevisiae can be highly beneficial for:
- Older horses
- Poor doers
- Horses who frequently travel or compete
- Changes in diet – including when the spring grass grows!
- During times of increased stress
- Horses who suffer from loose droppings or conditions such as faecal water syndrome
- After worming or antibiotic treatment
- Changes in routine
Understanding colony-forming units
If you’ve ever looked at gut support supplements before, you’ve probably seen that S. cerevisiae is measured in CFU rather than milligrams or grams. CFU stands for colony-forming unit, a microbiological unit used to estimate the number of viable cells that can multiply to form a colony. The higher the number of CFU of an ingredient, the higher the number of viable cells that will enter the hindgut. A lower CFU means that less cells are viable, and the ingredient is therefore less effective.
Because microbial samples contain extremely large numbers of viable cells (sometimes billions!), CFU is expressed as a scientific notation, such as 2 x 1011.
An evolving ingredient
There is still much that we don’t know about the equine hindgut, so research is ongoing and continuously evolving. A recent study by Sandrini et al. (2025) found that S. cerevisiae may benefit horses with insulin resistance, as whilst it improves fibre digestibility it does not affect total energy digestibility. There is still a lot of research needed in this area to determine the mechanisms behind the effect that yeast has on insulin resistance, but researchers have already stated interest in further exploration.
Other studies have found that supplementing with live yeast can have anti-inflammatory effects, with some studies even finding that exercise performance was enhanced after supplementation. One such investigation found that supplementing with S. cerevisiae reduced exercise-induced cellular stress, suggesting that dietary mitigation of excessive inflammation may be achievable (Valigura et al., 2021).
Take away
S. cerevisiae is a scientifically established yeast ingredient used in equine nutrition to support hindgut stability and fermentation balance. In a digestive system that relies heavily on microbial activity to extract energy from fibre, maintenance is fundamental.
By supporting these conditions, this live yeast can contribute to digestive reliability across a range of management and performance demands and remains a cornerstone of effective nutritional support for all horses.
If you would like to learn more about the equine hindgut and the role that pre and probiotics play in supporting its function, click here.
Written by Anna Jones BSc (Hons) Equine Science – Customer Care & Marketing Associate
References
Ganda, E., Chakrabarti, A., Sardi, M. I., Tench, M., Kozlowicz, B. K., Norton, S. A., Warren, L. K., & Ehsan Khafipour. (2023). Saccharomyces cerevisiae fermentation product improves robustness of equine gut microbiome upon stress. Frontiers in Veterinary Science, 10. https://doi.org/10.3389/fvets.2023.1134092
Jouany, J.-P. ., Medina, B., Bertin, G., & Julliand, V. (2009). Effect of live yeast culture supplementation on hindgut microbial communities and their polysaccharidase and glycoside hydrolase activities in horses fed a high-fiber or high-starch diet. Journal of Animal Science, 87(9), 2844–2852. https://doi.org/10.2527/jas.2008-1602
Mackenthun, E., Coenen, M., & I. Vervuert. (2013). Effects of Saccharomyces cerevisiae supplementation on apparent total tract diges tibility of nutrients and fermentation profile in healthy horses. Journal of Animal Physiology and Animal Nutrition, 97(s1), 115–120. https://doi.org/10.1111/jpn.12043
Mona M.Y. Elghandour, Juan Carlos Vázquez-Chagoyán, Abdelfattah Z.M. Salem, Kholif, A. E., José Simón Martínez Castañeda, Camacho, L. M., & Buendía, G. (2014). In Vitro Fermentative Capacity of Equine Fecal Inocula of 9 fibrous Forages in the Presence of Different Doses of Saccharomyces cerevisiae. 34(5), 619–625. https://doi.org/10.1016/j.jevs.2013.11.013
Sandrini, S., Perricone, V., Pea, A., Cenati, C., Savoini, G., Baldi, G., & Agazzi, A. (2025). Live yeast supplementation improves apparent nutrient digestibility of high-fibre diet in mature quarter horses. Italian Journal of Animal Science, 24(1), 1381–1389. https://doi.org/10.1080/1828051x.2025.2515539
Valigura, H. C., Leatherwood, J. L., Martinez, R. E., Norton, S. A., & White-Springer, S. H. (2021). Dietary supplementation of a Saccharomyces cerevisiae fermentation product attenuates exercise-induced stress markers in young horses. Journal of Animal Science, 99(8). https://doi.org/10.1093/jas/skab199