An invisible universe
Prof.ssa Emanuela Valle
Dip. Scienze Veterinarie – Università di Torino
Full Professor – EBVS® European Specialist in Veterinary and Comparative Nutrition
If we think of the horse as an organism made up of billions of cells, we should know that something even bigger lives inside him: the microorganisms in his intestines are likely to outnumber his own cells.
Bacteria, yeasts, and microscopic fungi coexist in balance in what we call the ‘gut microbiome,’ a complex and fragile ecosystem, capable of influencing not only digestion, but also metabolism, immune system, and even the horse’s behaviour.
This invisible community effectively represents a ‘metaorgan,’ a set of organisms that work in synergy with the host.
The microbiome actively participates in digestion, regulates the immune response, and communicates with the central nervous system through biochemical signals that connect the gut to the brain.
This is why today there is increasing talk of the ‘microbiome as a functional organ,’ capable of profoundly influencing health, energy, and behaviour.
In recent years, thanks to modern next-generation genetic sequencing techniques, research has revealed that every horse hosts its own unique microbial world, like a true biological fingerprint.
A delicate balance
Trillions of microorganisms live in the horse’s large intestine, working together to ferment vegetable fibre, transforming it into energy. This fermentation produces volatile fatty acids, including butyrate, a valuable molecule that nourishes intestinal cells and has anti-inflammatory and antioxidant effects. The microbiome’s activity doesn’t stop there, it competes with pathogenic bacteria, preventing them from multiplying.
It strengthens the immune system, stimulating balanced responses.
It communicates constantly with the horse’s brain through the so-called gut-brain axis, which started to the well known expression ‘gut decision,’ which we now know has a scientific basis.
When the balance is disrupted
Stress, transportation, dietary changes, or excessive grain intake can disrupt this balance, leading to a condition called intestinal dysbiosis: some microbial populations become too dominant, while beneficial ones decline.
The horse’s microbiome has extremely ‘low margin for error’: its core microbiome, the group of microorganisms common to all healthy individuals, is surprisingly small.
This means that little is needed to alter it, but also that a lot can be done to keep it stable.
The key to a healthy microbiome
Nutrition and well-being are the keys to a healthy microbiome.
The first way to care for the microbiome is to respect the horse’s nature.
Fibre, fibre, and more fibre: hay and forage are the ideal and essential food for nourishing the good bacteria in the gut.
Low starch: Excess grain intake reduces beneficial species and alters intestinal pH.
Routine and tranquility: Stress and sudden dietary changes can compromise the microbial balance more than you might think.
Prebiotics, probiotics, and symbiotics: small invisible allies
In addition to good dietary management, nowadays equine nutrition offers useful tools to support microbial activity during times of greatest need, such as travel, competition, or seasonal changes.
Prebiotics
These are substances that selectively nourish beneficial microorganisms, promoting their growth. Among these, fructooligosaccharides (FOS) and inulin, found in chicory and many grazing land, represent valuable natural sources.
Probiotics
These are live or inactivated microorganisms that directly contribute to the balance of the microbiome.
‘Saccharomyces cerevisiae,’ for example, is a yeast widely studied for its ability to improve fibre digestion and stimulate the metabolism of beneficial bacteria.
Symbiotics
When prebiotics and probiotics are combined, a synergistic (symbiotic) effect is achieved, increasing the stability of the intestinal flora and the ability of microorganisms to survive and function effectively.
Beneficial fermentation
Some new-generation supplements contain fermentation products, derived from natural sources of enzymes that improve digestion and nutrient absorption, reducing gas formation and abnormal fermentations.
Combined with yeasts such as Saccharomyces cerevisiae and prebiotic fibres such as chicory inulin, these substances help maintain a stable microbiome.
The presence of vitamins such as fat-soluble vitamins and plant extracts with antioxidant effects help protect the mucous membranes and strengthen the horse’s natural defenses.