Horses are herbivores and their digestive systems have evolved over many years to consume an almost continuous supply of fibrous feed which is digested within the hindgut (caecum and colon) by billions of microbes living in the hindgut through a process known as fermentation.
Whilst the entire gastrointestinal tract (GIT) of horses is a complex ecosystem teeming with a diverse array of microorganisms, the highest numbers are present in the hindgut. Collectively known as the hindgut microbiome, these microbes play a crucial role in the digestion and overall health of your horse. Recent research has shed light on the intricate relationship between the gut microbiota and the immune system, revealing how this connection impacts equine health and disease.
In our latest technical blog, Lisa Elliott MSc – Equine Nutrition Solutions, explores the equine gut microbiota’s influence on immunity, and how you can help protect and nurture your horse’s microbiome for optimum health.
Microbes and Immune Homeostasis
The gut microbiota is in constant interaction with your horse’s immune system. This interaction is vital for maintaining immune homeostasis and preventing inflammation. The gut microbiome influences various immune functions, including the regulation of inflammation, energy metabolism, and the maintenance of a balanced immune response.
Additionally, research has shown that gut microbes are involved in blood vessel development and help strengthen and stimulate the immune system. The gut microbes are also a critical line of resistance to invading pathogenic or disease-causing microorganisms. This is known as the ‘barrier effect’, and it means that harmful bacteria are competitively excluded, which helps to prevent serious illness and disease.
The Role of Specific Microbes in Immune Regulation
Research has shown that certain types of bacteria within the hindgut have specific roles within overall health and immunity, meaning that immunity can be significantly influenced by the types of microbes present. For example, certain bacterial families like Ruminococcaceae who are associated with fibre digestion, are known to have immune regulatory properties. These bacteria also produce short-chain fatty acids (SCFAs) like butyrate, which have protective functions on the gut wall and can modulate immune responses.
Additionally, certain microbes have been identified as key players in immune regulation. For instance, the genus Akkermansia is known for its anti-inflammatory properties and its role in maintaining gut barrier integrity. Similarly, members of the Clostridiales order have been linked to the expression of immune-regulatory genes, suggesting their involvement in maintaining immune balance. Identifying these ‘microbial biomarkers’ of health or disease is essential for anticipating potential problems and developing targeted nutritional approaches for optimum immunity.
Impact of Diet on Gut Microbiota and Immunity
Diet plays a significant role in shaping the hindgut microbiome. Whilst a healthy, well-balanced microbe population has huge benefits for your horse, any disturbance to the microbial equilibrium can have the opposite effect and be potentially harmful. Horse’s diets, particularly the consumption of starch, fibre, and fat, can significantly impact the composition of their gut microbiome and changes in diet can lead to shifts in microbial populations, which in turn can affect immune function.
Certain situations such as excessive cereal starch reaching the hindgut or sudden dietary changes, for example from hay to lush pasture can result in microbial imbalances or ‘dysbiosis’ which can invariably lead to hindgut acidosis. Hindgut acidosis is a consequence of the rapid growth of certain types of lactic acid producing bacteria. The increased lactic acid causes a drop in pH and results in a more acidic environment and can lead to inflammation of the hindgut membrane and potentially laminitis or colic, which are associated with systemic inflammation.
Impact of Age and Stress on Gut Microbiota
Age, breed, stress during competitions, transportation, and exercise also influence the equine gut microbiome. Foals acquire their initial gut microbiota from their mothers and the environment, and this microbial community evolves as they grow. Stressful events, such as weaning, transportation and competition can disrupt the gut microbiota, leading to immune dysregulation and increased susceptibility to disease.
Feeding to Nurture the Microbiome and Support Optimum Immunity
To optimise your horse’s immunity and prevent disease, you need to nurture the right microbes through the right diet and feed management.
Fibre and Diversity
The foundation of maintaining the happiest and healthiest hindgut microbes lies in feeding an abundance of high-quality, ad-lib fibre. Fibre supports microbial balance, encourages the proliferation of fibre-digesting, beneficial bacteria, and research has shown that horses consuming fibre-rich diets have a more stable microbial community. A stable microbial population contributes to a healthier horse, and maximises immunity, making a fibre-focused diet essential for promoting this stability.
Recent studies (Dougal et al., 2013; Costa et al., 2012) have highlighted the diverse range of bacterial species within the equine hindgut microbiome. This diversity is a hallmark of a healthy microbiome, whereas a loss in diversity has been linked to digestive issues and imbalances.
Feeding a varied diet promotes microbial diversity, which in turn supports a healthy hindgut. Coligone Fibre Cubes, fed alongside forage, can enhance your horse’s fibre intake and introduce greater fibre variety, promoting better hindgut health. Additionally, the fibre within Coligone Fibre Cubes support butyrate producing microbes, to help maintain gut wall integrity and support optimum immunity.
Providing good quality forage and digestible fibre sources like Coligone Fibre Cubes will also help meet your horse’s energy needs without relying on starch from cereals. Minimal starch and higher fibre will reduce the potential for starch to reach the hindgut and create imbalances, helping to keep the gut microbes healthier and more balanced to further promote optimum health and immunity.
Dietary Change
Gradual dietary changes are crucial for maintaining microbial health to help maximise immunity. Abrupt changes are a leading cause of microbial imbalances, known as dysbiosis. Whether switching from a mix to a cube, changing balancers, or transitioning between seasonal grazing (e.g., from winter hay to lush summer grass), all changes should be introduced slowly over at least two weeks. This gradual approach allows gut microbes to adapt, preserving stability and health. During periods of dietary transition, feeding Coligone Powder or Liquid can help buffer acid levels and maintain a stable gut pH, supporting a balanced, healthy microbiome.
Probiotics and Prebiotics
Probiotics are thought to promote microbial health by introducing certain live microbes to improve and support the hindgut microbe population. Yeasts in the form of yeast cultures, such as Yea-sacc, have been shown to stimulate fibre-digesting, beneficial bacteria and increase fibre digestibility.
Prebiotics work differently to probiotics in that they provide a food source for beneficial bacteria and help to encourage their growth.
ScFOS prebiotics provide food for beneficial bacteria and several studies have shown that ScFOS can help mitigate disruptions to the hindgut microbes and restore a healthy equilibrium.
MOS works in a slightly different way to ScFOS, but it can bind to invading pathogenic microbes and take them out of the hindgut, helping to encourage growth of beneficial microbes, promote a healthy microbial balance and support your horse’s immunity.
Recent research (Lindeberg et al. 2021) has shown that when pregnant mares and foals were fed a controlled level of oligosaccharides (MOS and FOS), foals had a higher abundance of Akkermansia species and increased abundance of several bacteria species which have been identified as being anti-inflammatory, further supporting the ability of FOS and MOS to help promote optimum immunity.
Coligone includes all three of these vital components—probiotics, ScFOS, and MOS—working synergistically to promote a healthy, stable hindgut microbiome and support optimum immunity.
Additionally, through the delivery of these key pro and prebiotics, Coligone Powder or liquid can also help stabilise the gut microbiome in stressful situations and acts as a calmer, helping your horse to stay calm and relaxed and minimising levels of stress that could disrupt the microbes and lead to dysbiosis.
The relationship between hindgut microbes and the immune system is dynamic and complex and understanding this relationship is essential for maximising your horse’s health and preventing diseases. By focusing on the gut microbiome, recognising how feeding can affect these microbes and knowing how to support a healthy, balanced microbiome through the right diet and nutrition, you can help support optimal daily health and immunity. As research in this field continues to evolve, it will help provide new insights into the intricate relationship between immunity and microbes in equine health, and how we can further promote immunity through informed and targeted nutrition.
