How can pre- and probiotics help to support horse health?

Horses have evolved to eat a high fibre diet. They rely on a population of microbes, predominantly bacteria but also include protozoa and fungi, in their hindgut, to ferment fibrous plants.

This fermentation results in the production of Volatile Fatty Acids (VFAs) such as acetate and butyrate, which are used as an energy source by the horse. In addition, these microorganisms also produce vitamins (e.g. B1, biotin and vitamin K), help to maintain gut movement and act as a barrier against harmful bacteria.

The microorganisms in the horse’s hindgut live in a delicate balance and can easily be disrupted by a number of factors such as stress, medication, starch overload, low forage diets and sudden dietary changes.
Pro- and Prebiotics have been the subject of increasing interest in equine nutrition, due to their potential positive impact on the gut microflora and therefore the horse’s overall health and wellbeing.

What are Prebiotics and Probiotics?

Probiotics: Are live microorganisms, so called, ‘good bacteria’, which, when fed in adequate amounts, improve the microbial balance of the digestive system. Currently only a few products, all of which contain Saccharomyces cerevisiae, are approved for use in horses in the European Union and the United Kingdom. Products containing other live bacteria (e.g. Bifidobacterium, Lactobacillus, Streptococcus, Enterococcus and Lactococcus species) are not currently licensed for use in equine feeds and supplements in the EU and UK.
Prebiotic: Are defined as ‘selectively fermented ingredients that allow specific changes, both in the composition and/or activity of the gastrointestinal (GI) microflora that confers benefits upon the host wellbeing and health’. In other words, they provide a food source for the ‘good’ cellulolytic bacteria in the horse’s hindgut. The most common prebiotics for horses include:

  • Inulin: a class of dietary fiber polysaccharides produced naturally by many types of plants such as chicory.
  • Fructo-oligosaccharide (FOS):  a naturally occurring short-chain fructo-oligosaccharides.
  • Mannan-oligosaccharides (MOS): mannan-based oligosaccharides derived from yeast cell walls.

How do Prebiotics and Probiotics work?

Despite the similar sounding names, pro- and prebiotics are actually very different, with unique mechanisms of action. The main benefit of probiotics is to help with the fermentation of fibre in the horse’s GI tract. This results in the production of VFAs, which provide an important energy source for the horse. The live ‘good’ microbes in probiotics also help to keep the ‘bad’ microbes (e.g. Salmonella spp.) from overpopulating the GI tract and causing problems such as diarrhoea.

Prebiotics, such as inulin and FOS, are non-digestible feed ingredients that provide a source of energy to beneficial microbes, thus allowing them to reproduce and increase in population. By enhancing the survival and viability of the natural flora of ‘good’ bacteria in the GI tract prebiotics help keep the ‘bad’ bacteria in check. The prebiotic MOS has a slightly different mode of action; it acts as a sticky sponge, clearing up the harmful bacteria and removing them from the digestive system.

When are probiotics and prebiotics useful?

Fibre, which is fermented by microbes in the hindgut is the foundation of the horse’s diet and therefore all horses may benefit from the inclusion of both pro- and prebiotics in their diet. However, in certain situations feeding pro- and prebiotics may be particularly helpful.

Horses in high levels of work (e.g. racehorses and competition horses) are often fed diets that provide high levels of hard feed, often rich in cereals, and low levels of forage. In addition, they are more likely to be exposed to stressful environments and may travel frequently, often over long-distances. All of these factors can adversely affect the balance and diversity of micro-flora in the gut. Providing pro- and prebiotics to these horses can help to reduce the risk of digestive issues and improve fibre digestion. As a result, the horse will get more nutrition from the forage portion of their diet and thus their requirements for hard feed will be reduced. Similarly, pro- and prebiotics can be immensely useful for horses that struggle to gain and maintain weight and condition, as they help to maximize digestive efficiency.

It is well known that sudden change in diet or management can cause digestive disturbances. However, studies have shown that feeding prebiotics can help mitigate against these intestinal microflora alterations. Whether introducing a different hard feed or moving to a new pasture, including probiotics and/or prebiotics in the diet may help to reduced disruptions of the delicate microbial population in the horse’s hindgut.

Horses suffering from clinical problems such as colic, grass sickness and starch-overload laminitis will invariably have unbalanced hindgut microflora and thus feeding pro- and prebiotic is recommended. However, even problems not associated with the GI tract can lead to changes in the normal microflora due to medication (e.g. antibiotics) or stress.

Although, feeding probiotics and prebiotic may help support the horse during times of illness or injury and aid recovery, we recommend speaking with our team of nutritionist before introducing any dietary changes.

Which Connolly’s Red Mills Feeds contain probiotics and prebiotics?

Feeds in the Connolly’s Red Mills Care range contain a unique Care package. This includes pure protected yeast, as well as the prebiotics FOS and MOS, all of which help to promote a healthy hindgut environment and promote overall wellbeing.

Find out more about the RED MILLS Care Range

What about supplements?

Depending on the individual horse and situation, a supplement containing prebiotics may also be beneficial.

Horses in hard work e.g. racehorses and competition horses, as well as individuals that tend to lack appetite may benefit from the addition on Foran Equine B-Complete to their diet. B-Complete is a comprehensive B-vitamin supplement, with added prebiotic. This palatable, liquid supplement aids blood cell formation, metabolism and energy production, as well as supporting digestive function and encouraging ‘eating up’.

Foran Equine Nutri-Gard Extra is ideal for horses prone to, or at risk of, gastric ulcers. It is high in digestible fibres, which help to coat the stomach lining. Prebiotics also help optimise digestion and feed utilisation. In addition, Foran Equine Nutri-Gard Extra contains hydrolysed protein to aid the immune system and B-vitamins to support metabolism.

Although probiotics are generally not recommended for young foals, specialist prebiotic supplements can be beneficial. Foran Equine Friska Foal is a multi-vitamin and prebiotic supplement specifically formulated to support the foal’s nutritional needs during times of illness or stress, such as travelling. Given by mouth once daily, Foran Equine Friska Foal is a pleasant tasting supplement suitable for all ages of foal; from newborn (24+hrs old) to weanlings.


We still have much to learn about the microflora in the horse’s gut and how this can be influences by both pro- and prebiotics. However, there is good scientific evidence that pro- and prebiotics can positively influence GI microflora and therefore help to support horse’s overall health and wellbeing.

If you would like to discuss your individual horse’s feed and management in more detail get in touch with the Connolly’s RED MILLS nutrition team for expert and practical advice.

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