When equine digestion and gut health are discussed, yeast, MOS, and beta-glucans are very often mentioned in the same context. The main reason for this is that MOS and beta-glucans are natural structural components of yeast, and research has shown that these three complement one another in different ways within the gut.
In this combination, yeast acts as a kind of “enabler,” MOS influences the interaction between the gut environment and bacteria, and beta-glucans are linked to the normal connection between the gut and the immune system. Together, they form a functional whole that has been extensively studied, particularly in connection with the horse’s fiber-based diet.
Yeast – Why Is It of Interest in Equine Digestion?
The horse’s digestive system relies heavily on microbial fermentation in the hindgut. Fiber from forage is not a direct source of energy for the horse; it must first be broken down by gut microbes. Yeast has been studied specifically from this perspective.
Numerous studies have found that the use of yeast products is associated with improved fiber digestibility and more efficient fermentation. This does not mean that yeast digests the feed on behalf of the horse, but rather that it helps create conditions in the gut where microbes can perform their function more effectively. For this reason, yeast has been studied especially in forage-based feeding and in situations where optimal gut function is critical (Glade, 1991; Medina et al., 2002; Graham-Thiers & Bowen, 2011; Journal of Equine Veterinary Science).
MOS – A Structure That Influences the Interaction Between the Gut Environment and Bacteria
MOS compounds, or mannan-oligosaccharides, are not live microbes. They are fibrous structures derived from the yeast cell wall that pass through the digestive tract without being absorbed. In research, MOS is of interest primarily because of its role in the interaction between bacteria and the gut environment.
In the scientific literature, MOS compounds have been studied from the perspective of bacterial adhesion mechanisms. In practice, this means that MOS structures may influence how certain bacteria behave in the gut and what they attach to. For this reason, MOS compounds are viewed as part of gut environment management rather than as rapidly fermentable fiber (Spring et al., 2000; Desrochers et al., 2005; Johnson, 2019; Journal of Animal Science).
Beta-Glucans – A Link Between the Gut and the Immune System
Beta-glucans are structural glucose chains found in the yeast cell wall. They differ from many other dietary fibers in that their structure is biologically recognized by the body. For this reason, beta-glucans are not of interest as an energy source, but rather for the way they participate in normal recognition and signaling mechanisms within the gut and the body as a whole.
In research, beta-glucans are often associated with the gut-associated immune system. A large part of the horse’s immune function operates through the gut, and beta-glucans have been found to be part of this normal interaction. This is not about preventing or treating disease, but about how the body recognizes structures and maintains normal immune readiness (Vetvicka & Oliveira, 2014; Delgado et al., 2012; Smith & Williams, 2018; Veterinary Immunology and Immunopathology).
Where Does the Horse Get Yeast, MOS, and Beta-Glucans?
Horses do not produce yeast, MOS compounds, or beta-glucans themselves; they are always obtained through the diet. Yeast is supplied through complementary feeds and yeast cultures—products that contain yeast as well as compounds formed during its growth. MOS and beta-glucans are present at the same time because they are natural components of the yeast cell wall. In some products, these cell wall structures are further concentrated.
Beta-glucans are also found in grains such as barley and oats, but these beta-glucans differ structurally from those derived from yeast and are not studied in the same way from a gut–immune interaction perspective.
Why Are These Studied Together?
Simply because they form a complementary whole. Yeast is primarily linked to fiber utilization and fermentation, MOS to the interaction between the gut environment and bacteria, and beta-glucans to the normal connection between the gut and immune function. In research, this combination is examined as a nutritional strategy (Respondek et al., 2008; Wagner et al., 2015; Equine Veterinary Education).
Practical Situations Where the Combination of Yeast, MOS, and Beta-Glucans Is Most Commonly Used
In research, the combination of yeast, MOS compounds, and beta-glucans is not viewed as a single “solution,” but rather as part of feeding strategies, particularly in situations where the horse’s digestion and gut environment are under greater-than-normal strain. In practice, these situations are often very routine.
Dietary Changes and Transition Periods
When the diet changes, the gut microbiota must adapt to a new feed composition. This applies, for example, to the transition to pasture, changes in forage, or adjustments in concentrate feeding. Research has linked yeast to situations where fiber-based fermentation and digestibility are key, while MOS and beta-glucan structures have been examined from the perspective of gut environment stability. During such transition periods, the primary concern is that microbial fermentation remains steady and predictable, without placing excessive strain on digestion (Glade, 1991; Medina et al., 2002; Respondek et al., 2008).
Seasonal Load and Competition Season
During competition and training seasons, horses are often exposed to several simultaneous stressors, such as physical exertion, transport, and environmental changes. In research, beta-glucans are highlighted in situations examining the normal interaction between the gut and immune system, while yeast has been studied in terms of overall feeding efficiency. In practice, this means an interest in feeding solutions that support the horse’s normal physiology during periods of increased workload (Vetvicka & Oliveira, 2014; Smith & Williams, 2018; Veterinary Immunology and Immunopathology).
Sensitive Gut and Digestive Balance
Horses show individual differences in digestive sensitivity. MOS compounds and beta-glucan structures have been studied particularly because they are not rapidly fermentable and do not sharply increase gas production. For this reason, they are of interest in situations where maintaining balance and control of the gut environment is more important than rapid energy intake. The role of yeast in this context relates primarily to supporting the functional conditions of hindgut microbes, rather than directly addressing digestive symptoms (Spring et al., 2000; Wagner et al., 2015; Equine Veterinary Education).
Supporting a Fiber-Based Diet
The horse’s natural diet is based on forage, but efficient fiber utilization is not a given. Research has linked yeast to fiber digestibility and fermentation efficiency, while MOS and beta-glucan structures have been examined as part of the gut environment’s structural framework. For this reason, this combination is particularly utilized when feeding focuses on high-quality forage and long-term gut functionality (Graham-Thiers & Bowen, 2011; Respondek et al., 2008).sacsac
References
- Glade, M. J. (1991). Yeast culture supplementation improves feed digestibility and performance in horses.
- Medina, M. et al. (2002). Effect of yeast culture supplementation on digestion in horses.
- Graham-Thiers, P. & Bowen, L. (2011). Impact of yeast supplementation on fiber digestibility in horses. Journal of Equine Veterinary Science.
- Respondek, F. et al. (2008). Prebiotic potential of yeast-derived products in horses. Journal of Animal Physiology and Animal Nutrition.
- Wagner, A. et al. (2015). Effects of prebiotics and yeast products on equine gastrointestinal health. Equine Veterinary Education.
- Spring, P. et al. (2000). Mannan-oligosaccharides reduce pathogen adhesion to the intestinal lining.
- Desrochers, A. et al. (2005). Effects of mannan-oligosaccharides on gut health and immunity. Journal of Animal Science.
- Vetvicka, V. & Oliveira, C. (2014). β-glucan effects on immune function in animals.
- Delgado, G. et al. (2012). Effects of β-glucans on intestinal immunity.
- Smith, J. & Williams, A. (2018). β-Glucans in equine immune function. Veterinary Immunology and Immunopathology.
