Your horse eats well, moves around, seems healthy – and yet sometimes something isn't quite right. Loose stools, restlessness, susceptibility to colic, coat problems. Symptoms that at first glance seem to have little to do with each other. On closer inspection, almost all of these issues lead to the same place: the gut.
The equine gut is one of the most fascinating and at the same time most sensitive systems in the animal kingdom. It is longer than a school bus, processes up to 15 kilograms of roughage daily – and reacts to the slightest changes. Understanding how this digestive tract truly functions allows you to understand your horse on an entirely new level.
This article is the foundational piece of our series "Equine Gut & Detoxification". No prior knowledge necessary – just curiosity.
A digestive system that wasn't planned that way – yet functions perfectly.
The horse is a steppe animal. Evolutionarily, it is designed to graze 16 to 18 hours a day – small amounts, continuously, primarily fibrous grass. The stomach is tiny relative to body size: just 10 to 15 liters capacity. For comparison: a cow has a rumen with 100 to 200 liters.
This means: the horse is not made for large meals. It is designed for continuous, small amounts of feed.
In modern husbandry systems, this often looks different – concentrated feed twice a day, several hours without roughage, little movement. It's no wonder that the gut gets out of balance.
The journey through the equine gut – station by station
1. The mouth and pharynx: Where it all begins
Even before food reaches the stomach, digestion begins in the mouth. Horses chew intensely – up to 3,000 chewing movements per hour with good hay. During this process, the food is mixed with saliva, which contains important buffer substances. This saliva neutralizes stomach acid. The more the horse chews, the better buffered its stomach is.
What this means: Little roughage = little chewing = little saliva = more stomach acid. Gastric ulcers often arise not from too much acid, but from too little buffering.
2. The stomach: Small but mighty
The horse's stomach continuously produces acid – even when it's empty. This makes evolutionary sense: in nature, it is never empty. In modern husbandry, it often is.
It has two areas: the non-glandular upper part (without mucosal protection) and the glandular lower part. Food residues that remain too long in an empty stomach can irritate the unprotected upper mucosa – this is one of the main reasons for gastric ulcers in horses.
Zeolite connection: Zeolite can adsorb excess acid and irritants in the stomach and soothe the mucous membranes – especially during periods of stress or change.
3. Small intestine: The fast track
From the stomach, the chyme enters the small intestine, which is about 20 to 25 meters long. Here, water-soluble nutrients are absorbed: protein, fats, simple carbohydrates, many vitamins and minerals.
The small intestine works quickly – its contents pass through in less than an hour. This is important to understand: too much starch at once (e.g., a large portion of concentrated feed) overloads the capacity of the small intestine. What isn't absorbed moves on to the large intestine – and starch should ideally not reach there.
4. The large intestine: The heart of equine nutrition
This is where the amazing things happen. The horse's large intestine – consisting of the cecum, colon, and rectum – holds 100 to 130 liters and hosts a vast community of microorganisms: bacteria, fungi, protozoa. Together, they form the microbiome.
These microorganisms ferment the indigestible crude fiber from hay and grasses into short-chain fatty acids – the horse's main energy source. The horse meets up to 70% of its energy needs this way.
The microbiome is not a constant, but a balance. And this balance is surprisingly fragile.
Impressive figures: The equine gut at a glance
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- Total length of the digestive tract: approx. 30 meters
- Stomach volume: 10–15 liters (only 8% of total volume)
- Large intestine volume: 100–130 liters
- Daily feed intake: 10–15 kg hay
- Daily saliva production: 30–40 liters
- Microorganisms in the large intestine: Several billion per milliliter of intestinal content
- Retention time in the large intestine: 36–72 hours
The microbiome – the underestimated world in the equine gut
When we talk about gut health in horses, we are primarily talking about the microbiome. This community of trillions of microorganisms is not only responsible for digestion. It influences the immune system, mood, metabolism – and susceptibility to diseases.
A healthy microbiome is diverse and balanced. Certain groups of bacteria keep others in check. Beneficial bacteria produce substances that strengthen the intestinal wall and inhibit inflammation.
What disrupts this balance?
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- Abrupt feed changes (especially during spring grazing)
- Large amounts of concentrated feed that introduce undigested starch into the large intestine
- Antibiotic treatments
- Stress (transport, competition stress, stable changes)
- Poor hay quality with mycotoxins
- Lack of exercise
- Long periods of fasting
The result: dysbiosis – a shift in balance towards unfavorable bacterial groups. And dysbiosis is the starting point for many of the problems horse owners face daily: loose stools, susceptibility to colic, immune deficiency, coat problems.
Why horses are so much more sensitive than other animals
This is explained anatomically. Unlike ruminants, horses do not have a rumen that acts as a buffer. Fermentation only takes place in the large intestine – after the stomach. This means:
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- Feeding errors directly affect the most sensitive part of the digestive tract
- The transition from fiber-based to starch-based nutrition is particularly risky
- Horses cannot vomit – what goes wrong in the stomach or intestine must pass through the intestine
- Changes in the microbiome can quickly lead to life-threatening colics
This is not a design flaw. It is the evolutionary answer to a niche: grazing steppe animals that continuously consume small amounts of simple food. The problem arises when we take them out of this niche.
The gut-brain axis in horses – more than just a gut feeling
Recent research shows: The gut and brain constantly communicate with each other – via the vagus nerve, via hormones, via neurotransmitters that the microbiome itself produces. In humans, this is called the gut-brain axis. In horses, this connection is at least as pronounced.
This explains why gut problems are often accompanied by behavioral abnormalities: restlessness, sensitivity, poor trainability. And it explains why stress – a reaction of the nervous system – directly impacts the gut.
A horse that is internally restless often also has a gut that is out of balance. And vice versa.
What zeolite has to do with it
Zeolite is a natural volcanic mineral with a unique lattice structure. This structure allows the mineral to act like a sponge – it can bind toxins, excess acids, mycotoxins, and fermentation gases and transport them out of the gut.
But zeolite does even more: it has an anti-inflammatory effect on the intestinal lining, supports the stabilization of the microbiome flora, and can improve stool consistency – especially in horses prone to loose stools.
So it doesn't target a single symptom, but the system – the balance of the gut.
In part 4 of this series, we will look at the research in more detail. Today, it's enough to know: the gut needs a stable environment. And zeolite can help protect this environment.
Frequently Asked Questions
★ Why is the equine gut so much more sensitive than that of a dog or cattle?
Horses are monogastric hindgut fermenters – meaning fermentation occurs in the large intestine, after the stomach, without a buffering rumen beforehand. Therefore, feeding errors have direct and rapid consequences.
★ What is the microbiome and why is it so important?
The microbiome is the community of billions of microorganisms in the horse's large intestine. It produces up to 70% of the horse's energy, strengthens the immune system, and protects the intestinal wall. A disturbed microbiome (dysbiosis) is often the origin of loose stools, colic, and immune problems.
★ How often should I change my horse's feed?
As rarely as possible – and if so, then slowly. Any feed change should be introduced over at least 10–14 days so that the microbiome can adapt.
★ Can zeolite be fed daily?
Yes. Zeolite can be used as a daily feed supplement. Our dosage recommendations can be found in the article: Feeding zeolite to horses – Dosage, application & practical tips.
★ My horse has loose stools – is that related to the gut?
Almost always. Loose stools are a sign that something in the large intestine is out of balance – be it the microbiome, the intestinal mucosa, or water balance. More on this in part 2 of this series.
Sources
[1] Gilroy, R. et al. (2022): Metagenomic investigation of the equine faecal microbiome reveals extensive taxonomic and functional diversity PeerJ, peer-reviewed, Open Access Genomic study on thoroughbred horses mapping the diversity of the hindgut microbiome and directly linking changes in its composition to colic, laminitis, and diarrhea. → https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8957277/
[2] Several Authors (2024): Current Understanding of Equine Gut Dysbiosis and Microbiota Manipulation Techniques Animals, MDPI, peer-reviewed, Open Access Current review paper on the state of research on equine dysbiosis – causes, consequences, and possibilities for restoring gut flora. Explicitly addresses stressors such as feed changes, antibiotics, and transport. → https://pmc.ncbi.nlm.nih.gov/articles/PMC10931082/
[3] NIMSS, US University Consortium (2023/2024): The Equine Microbiome – NE2202 Research Project Institutional Research Documentation Coordinated research program of several US universities. Primary source for the statement that approx. 70% of the horse's energy requirements are met by microbial fermentation products in the large intestine. → https://nimss.org/projects/view/mrp/outline/18869
[4] Auburn University College of Veterinary Medicine (2023): Diagnosing Equine Gastric Ulcers Explains the continuous acid production of the equine stomach and why it continues – unlike in humans – even when empty. Includes prevalence data: up to 90% of racehorses and 60% of performance horses are affected. → https://www.vetmed.auburn.edu/blog/cvm-news/diagnosing-equine-gastric-ulcers/
[5] Valpotić, H. et al. (2017): Clinoptilolite nanoporous feed additive for animals of veterinary importance: potentials and limitations Periodicum Biologorum, peer-reviewed Review paper on clinoptilolite zeolite as a feed additive in farm animals. Documents the binding of mycotoxins, ammonium, and heavy metals in the gut, as well as anti-inflammatory effects on the intestinal mucosa. → https://hrcak.srce.hr/file/274435
More from the series: Equine Gut & Detoxification
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All parts of the series: • Part 1: The Horse's Gut – How it Really Works ← you are here • Part 2: Signs Your Horse Has Gut Problems – 12 Warning Signals • Part 3: Mycotoxins in the Equine Gut – The Silent Risk in Hay • Part 4: Zeolite and the Equine Gut – What Animal Research and Practice Confirm Together ← coming soon • Part 5: Gut Cure for Horses – Step-by-Step Program with Zeolite ← coming soon |
⭕️ Read more:
Zeolite - everything you need to know about feeding horses: Q&A and guide Feeding zeolite to horses – Dosage, application & practical tips
