What are probiotics? A probiotic is a microorganism introduced into the horse's body for its beneficial qualities. They are live bacteria or yeasts, often called 'good' bacteria. Horse probiotic supplements improve the health and the population of ‘good microbes’ in a horse's  hindgut. This boosts the horse’s natural defences and improves recovery after illness.

What are ‘good microbes’ and what do they do?

A horse’s hindgut consists of the cecum and the colon. Within these organs is a large population of good microbes, which includes bacteria, protozoa and fungi.

These microbes perform essential duties that keep a horse healthy. Including; breaking down food, consuming and excreting various substances and producing vitamins, amino acids and nutrients.

Intestinal flora also protects the horse from harmful pathogens. Either by attaching to the gut wall to prevent pathogens using it as a gateway to spread disease within the horse. Or by producing lactic acid to maintain an acidity level that promotes good microbes but is detrimental to harmful microbes.

'Good' bacteria must be healthy and plentiful for these actions to be effective and efficient.

Hindgut Environment

The environment in the gut is vital to microbe survival.

The pH balance (acid/alkaline) must be maintained within a narrow range for beneficial microbes to survive. They can deplete or increase depending on the environment they live in.

Different microbes also thrive on different diets. For example; some thrive on a diet high in hay whilst others thrive on a diet high in grass. Fluctuations of these microbes are subtle and the body manages them to no detriment.

When changes occur in favour of harmful microbes, the consequences can be damaging to the horse. For example; high grain diets increase levels of starch in a horse’s digestive tract. High levels of starch overload the stomach and small intestine and pass into the hindgut.

This causes an increase in certain harmful microbes, an increase in lactic acid production and a depletion of beneficial microbes. This can lead to digestive issues or the onset of disease.

Horse Probiotic supplements vs. Prebiotics


Probiotics are dietary supplements that contain live microorganisms, usually bacteria but sometimes yeast and fungi.


Prebiotics are not live organisms, they are food ingredients that stimulate growth and activity of intestinal flora. Bacteria themselves can have a prebiotic effect if they produce byproducts that in turn nourish other bacteria.

Natural Defences Boosted

Most fluctuations in intestinal flora will correct with time. The idea of probiotics is to introduce good microbes back into the gut and boost recovery.

By restoring the balance sooner, we can potentially prevent or reduce consequences of an imbalance.

When to use horse probiotic supplements

It is generally accepted that giving probiotics to healthy horses will make no difference to them as their intestinal flora is already well balanced.

Research into equine probiotics is ongoing but there is general agreement that they can be useful in the following circumstances:

  • Foals are not born with 'good' bacteria or any intestinal flora. They must acquire theirs from the environment around them and probiotics can help ensure the correct balance right from the start. 

  • Various illnesses can cause damage to intestinal flora. Probiotics are thought to boost the population again and prevent recurrence.

  • Dietary changes, diets low in roughage or high in grains upset the acid level in the gut. This can deplete microbe populations and encourage disease.

  • The ingredients in antibiotics are damaging to both harmful and helpful microbes. Probiotics can be used post antibiotics treatment to restore preexisting levels.

  • Stress or strenuous exercise can produce changes in hormone levels, body temperature, heart rate and other functions. All of which deplete microbes. Starting on a probiotic in the lead up to a stressful event may prevent or reduce problems.
  • Side effects and Dosage of Horse Probiotic Supplements

Probiotics have no known side effects.

It is important to deliver the dosage as recommended by the producer or you may not see any benefits. It is also important to note that you will not likely see any changes immediately. Always refer to the label for the length of time you should treat your horse.

To quickly and easily order probiotics for your horse online - check out AbActive, the best probiotic for horses from here.