The equine gut-brain axis: the link between mind and microbes
The connection between gut health and mental wellbeing – known as the gut-brain axis – is a hot topic in human health. But this same two-way communication system plays a vital role in the horse as well.
In fact, understanding how the digestive system and nervous system interact can unlock powerful insights into equine behaviour, performance, stress resilience and overall health.
At the heart of this system lies the microbiome, a diverse and dynamic community of microbes that do far more than just help digest fibre. These microbes are key players in immune function, inflammation regulation, nutrient absorption and the production of neurotransmitters and other signalling molecules that influence the brain.
What is the gut-brain axis?
The gut-brain axis refers to the constant, bidirectional communication between the gastrointestinal tract and the central nervous system. This link operates through a complex network involving:
- The vagus nerve, which sends signals directly between the brain and gut
- The enteric nervous system, often called the ‘second brain’ in the gut wall
- The immune system, which can respond to stress or dysbiosis with inflammation
- Gut microbes, which help regulate mood-related compounds like serotonin, dopamine and GABA (a neurotransmitter that helps regulates mood and promotes relaxation)
- Gut integrity – Chronic stress (in any form) can negatively impact the integrity of the gut’s epithelial lining, which plays an important role in maintaining balance in the microbiome and wider body systems. If this barrier breaks down, it can result in microbial dysbiosis and leaky gut – leading to more problems systemically such as inflammation, metabolic disease, laminitis, poor recovery and behavioural/mood changes.
When the gut is healthy, this system works in harmony and promotes calm, focus and physiological balance. But when the microbial balance and, in turn gut integrity, within the hindgut is disrupted, it can trigger a cascade of negative effects – not just on digestion but on behaviour, stress response and mental resilience.
The hindgut: more than just a digestive organ
In horses, the hindgut (comprising the caecum and colon) plays a critical role in fermenting fibrous material and producing volatile fatty acids and other key metabolites that fuel the horse’s energy needs. But it also serves as the main hub of microbial activity.
This microbial ecosystem is incredibly sensitive to change. Factors such as diet shifts, transport, antibiotic use, pain, stress (mental and physical), social disruption or even inadequate forage intake can disturb this balance, also known as dysbiosis.
When dysbiosis occurs, beneficial microbes decline while opportunistic or harmful bacteria may thrive. This imbalance can lead to gut inflammation, causing the epithelial lining to break down and leading to leaky gut syndrome. This alters nutrient absorption and releases compounds that negatively affect mood and behaviour via the gut-brain axis.
Signs the gut-brain axis may be under strain
When the gut and brain aren’t communicating well, the signs can show up in both the body and behaviour of the horse. Common red flags include:
- Heightened sensitivity or reactivity
- Difficulty concentrating during work
- Changes in mood or social behaviour
- Sudden reluctance to load, travel or engage
- Unexplained weight loss or changes in manure
- Increased frequency of stress-related health issues like ulcers or colic
These signs may not be immediately linked to gut health, but the gut-brain axis means that internal imbalance can express itself externally, often in subtle ways.
Supporting a healthy gut-brain connection
Maintaining balance in the gut microbiome is one of the most effective ways to support a calm, focused and resilient horse. Strategies include:
- Consistent access to high-quality forage: Fibre fuels the hindgut microbes and keeps fermentation steady
- Limit high-starch feeds: Excess starch can disrupt the microbial balance and lower hindgut pH
- Reduce unnecessary stressors: Routine, herd interaction and stable environments support emotional and gut stability.
- Give the horse time to adapt: Changes to workload, competition schedule, yard, rider or other routines can initiate a stress response. As such, they should be done slowly to allow the microbiome and other body systems time to adapt.
- Introducing targeted microbial support: Actisaf® live yeast probiotic can help restore microbial balance, in turn helping to support gut-brain communication
- Avoiding unnecessary medications: Antibiotics and NSAIDs can harm beneficial microbes, so use these only when necessary and always with veterinary guidance
A whole-horse perspective
The gut-brain axis is a powerful reminder that physical and mental health in horses are deeply connected. By supporting the hindgut microbiome, we’re not just improving digestion - we’re also nurturing the horse’s natural ability to cope with stress, perform consistently and remain engaged and comfortable in their work.
As science continues to uncover more about this complex connection, one thing is clear: a healthy gut means a healthier, happier horse both inside and out.
