The horse's intestines are important for digestion and converting fibre into the volatile fatty acids acetate, butyrate and propionate. These volatile fatty acids provide the horse with energy required for body maintenance, and metabolic processes and are used as fuel for the body during exercise. Fibre is fermented in the intestines by microorganisms. These micro-organisms are also known as the hindgut microbiome. The composition of the hindgut microbiome is important for fibre digestion, intestinal function, and the horse's immune system. Pre and probiotics are added to the diet to support the balance of the horse's microbiome and health.
The horse's digestive system can be divided into the foregut and hindgut. The foregut consists of the mouth, oesophagus and stomach. The small intestine, large intestine blind gut and rectum are known as the hindgut. In the horse's hindgut, multiple microorganisms make up the hindgut microbiome. The microbiome consists of various micro-organisms such as bacteria and fungi 1. The composition of the microbiome is unique for each horse. There are similarities in this composition between each horse, but generally every horse has its own unique composition 2. The composition and balance of the microbiome are important for fibre digestion 3. Nutrition has a strong influence on this composition 3. The composition of the microbiome is very susceptible to (abrupt) changes. A diet containing too much sugar and starch or abrupt changes to the diet are factors that affect the balance of the microbiome 3,4. This can lead to dysbiosis, where the balance of gut flora is disrupted, creating an inhospitable environment for "good" bacteria. Because the gut flora affects the immune system, among other things, dysbiosis affects the horse's health. Research results suggest that dysbiosis increases the risk of developing laminitis and colic 5. To support the horse's microbiome, and thus the functioning of the gut, but also the immune system pre and probiotic supplements are used.
Prebiotics
Prebiotics are non-digestible nutrients, such as carbohydrates in the form of fibre, which are fermented in the hindgut by microorganisms into short-chain fatty acids (SCFAs) including volatile fatty acid 6. Short-chain fatty acids (SCFAs) are important for hindgut health and immune system function 6. The addition of prebiotics therefore supports and promotes gut flora diversity and balance.
The most commonly used forms of prebiotics are inulin, fructooligosaccharides (FOS), mannan oligosaccharides (MOS) and galactooligosaccharides (GOS) 7,8. Fructooligosaccharides are the most researched form of prebiotic. Supplementing a combination of FOS and MOS has been shown to have a positive effect on the digestibility of dry matter, crude protein, and NDF in horses fed a high-fibre diet 9. In addition, FOS has a positive effect on the balance of the microbiome when the horse's diet changes abruptly. When the diet changes abruptly, or contains excess sugar and starch, supplementing FOS also has a positive effect on the composition and function of the microbiome. Vendrig et al (2013) showed that supplementation of GOS, among others, to the diets of adult warmblood horses has a positive significant effect on immune system function.
Probiotics
Besides prebiotics, probiotics are also (increasingly) used to support the hindgut microbiome. Probiotics consist of live microorganisms that, through supplementation, have a positive impact on the balance of the microbiome. The most commonly used form of probiotics comes from the yeast strain Saccharomyces cerevisiae 10. The bacteria strains Enterococci, Lactobacillus and Bifidobacterium are also used 2. However, these bacterial species are only present in small amounts in the horse's gut compared to other bacterial species.
Nerlich et al. (2018) studied the impact of Saccharomyces cerevisiae on the digestibility of various nutrients in the horse's diet. Results showed that supplementation of Saccharomyces cerevisiae had a positive effect on fibre digestibility (ADF) which then affects forage digestibility. Supplementation of this therefore also has a positive effect on hindgut health of the horse. Another study showed that the use of Lactobacillus and Bifidobacterium in foals, aged 0 to 20 weeks, resulted in a lower number of foals suffering from diarrhoea symptoms 11.
Thus, the use of pre and probiotics has a positive effect on the microbiome and thus intestinal function but also the immune system and health of the horse. Synovium Immunomodulator therefore contains probiotic brewer's yeast and Synovium Gastrosafe contains FOS.
References
1. Chaucheyras-Durand, F., Sacy, A., Karges, K., Apper, E. (2022) Gastro-Intestinal Microbiota in Equines and Its Role in Health and Disease: The Black Box Opens. Microorganisms,
10:1-33.
2. Schoster, A., Weese J,S., Guardabassi, L. (2014) Probiotic use in horses - what is the
evidence for their clinical efficacy? Journal of Veterinary International Medicine, 28(6):1640-
1652.
3. Julliand, V., Grimm, P. (2017) The Impact of Diet on the Hindgut Microbiome. Journal of
Equine Veterinary Science, 52: 23-28.
4. Dougal, K., de la Fuente, G., Harris, P.A., et al. (2014) Characterisation of the Faecal
Bacterial Community in Adult and Elderly Horses Fed a High Fibre, High Oil or High
Starch Diet Using 454 Pyrosequencing. PLOS ONE, 9(2):1-9.
5. Milinovich, G.J., Klieve, A.V., Pollitt, C.C., Trott, D.J. (2010) Microbial Events in the Hindgut
Effects of turmeric on equine hindgut During Carbohydrate-induced Equine Laminitis.
Veterinary Clinics of North America: Equine Practice, 26(1):79-94.
6. Davani-Davari, D., Negahdaripour, M., Karimzadeh, I., et al. (2019) Prebiotics: Definition,
Types, Sources, Mechanisms, and Clinical Applications. Foods, 8(92):1-27.
7. Cooke, C.G., Gibb, Z., Grupen, C.G., Harnett, J.E. (2023) Prebiotics and Synbiotics in
Equine Health and Disease. International Journal of Equine Science, 2(2):37-47.
8. Vendrig, J.C., Coffeng, L.E., Fink-Gremmels, J. (2013) In vitro evaluation of defined
oligosaccharide fractions in an equine model of inflammation. BMC Veterinary Research,
9(147):1-10.
9. Saeidi, E., Yarahmadi, H.M., Fakhraei, J., Mojahedi, S. (2021) Effect of Feeding
Fructooligosaccharides and Enterococcus faecium and Their Interaction on Digestibility,
Blood, and Immune Parameters of Adult Horses. Journal of Equine Veterinary Science,
99:1-6.
10.Nerlich, H.K., Koler, R., Powell, E., Williams, T.L. (2018) Saccharomyces Cerevisiae
Supplementations Effect on Fiber Digestibility in Equine. Journal of Animal Science,
96(2):266.
11.Tanabe, S., Suzuki, T., Wasano, Y., et al. (2014) Anti-inflammatory and Intestinal Barrier–
protective Activities of Commensal Lactobacilli and Bifidobacteria in Thoroughbreds:
Role of Probiotics in Diarrhea Prevention in Neonatal Thoroughbreds. Journal of Equine
Science, 25(2):37-43.
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