Our horse’s gastrointestinal (GI) system, or ‘gut,’ communicates with their brain through multiple channels. One of these pathways involves their immune system, which is aided by their gut microbiota. A horse’s gut microbiota is a complex, dynamic community of microbes, predominantly bacteria, but also archaea, protozoa, fungi and viruses. A healthy horse has an estimated 2-4 quadrillion bacteria in their gut!
The composition of our hose’s gut microbiota has a profound impact on their behaviour and health. This is mediated through the gut-brain-immune axis. Changes in the composition of their gut microbiota can influence neurotransmitter production and function. Neurotransmitters are the natural chemical messengers which have important roles influencing many processes in our horses. Temperament, behaviour, motor control, learning patterns and digestive function are all influenced by neurotransmitters. Gut microbial population also affects neuroinflammation (inflammation of the brain and spinal cord), which can further influence mood and behaviour. Excessive levels of neuroinflammation may worsen stress, anxiety, tension and irritation in our horses.
Many things can adversely affect our horse’s gut microbiota, which may contribute to dysfunction of the gut-brain-immune axis. Clinical signs, changes and conditions we may see in our horses when their gut-brain-immune axis has been disrupted include:
- Faecal water syndrome
- Gastric ulcers
- Colonic ulcers
- Failure to thrive
- Failure to put on/maintain weight
- Susceptibility to infections and/or recurrent, chronic infections
- Nervousness, erratic behaviour, shying, anxiety, irritability
- Equine metabolic syndrome
- Insulin resistance
- Inflammatory bowel disease
- Colic
- Scours/diarrhoea
- Laminitis
- Osteoarthritis
- Equine Asthma Syndrome
- Recurrent skin conditions
- Poor recovery post exercise, training and/or competition
- Excessive muscle tension
In some horses, however, dysbiosis (unhealthy balance of the microbial community in the gut microbiota) may result in no obvious outward signs, yet their health is likely impacted under the surface, and this may become evident further down the track. Many of the signs associated with a dysfunctional gut-brain-immune axis health are non-specific, meaning they can often be dismissed or attributed to something else. Unfortunatel,y this means that often the underlying cause(s) of the condition or clinical signs can be overlooked in our horses.
Some of the factors which compromise GI health, and in turn influence immune health and behaviour include (but are certainly not limited to): insufficient dry matter (long-stem) fibre in the diet; large sized ‘hard feeds’ (ie concentrates and grains); large percentages of starch and/or sugar in the diet; abrupt changes in diet and/or pasture; the use of certain medications (including antibiotics, non-steroidal anti-inflammatory drugs (NSAIDs), corticosteroids and ulcer medications); viral and/or bacterial infections; high parasite burdens; nutritional insufficiencies, deficiencies and/or excesses (usually certain minerals, but sometimes particular vitamins); heavy metal toxicities; stress; pain; dehydration; high levels of inflammation in the body; extended travel; intense exercise.
Given the modern demands, management, feeding and medication use in horses, most horses will have compromises to their gut microbiota. The effects of these can be long-lasting, unless specific, targeted, supportive and corrective action is taken. This is crucial not only for their GI health, but in turn their immune health and behaviour, in addition to their overall health, performance and recovery.
Camilla Whishaw is a highly regarded, experienced horsewoman and naturopath, helping to holistically treat and manage a broad range of equine health conditions and injuries, with a passion for mare and stallion fertility.
As a world-renowned practitioner, presenter, author, and consultant in the field of Equine Naturopathy, Camilla shares her knowledge through keynote presentations, interviews, lectures, panel sessions, and workshop training.
