The Equine Digestive System – A Rich and Fragile Ecosystem

Most of us associate yeast with making bread or as a by-product of brewing beer, but its probiotic properties also play an important role in the digestion process of horses.

The way we keep our horses is completely different to the way they would live in the wild and unfortunately this has a major impact on their extremely sensitive digestive system, often leading to serious gut issues.

Research shows that supplementing yeast has shown significant benefits in horses at all stages of life, enhancing their ability to digest feed, improving health and wellbeing.

Anyone who has owned a horse is aware of how “sensitive” the horse’s digestive system is. “Colic” has become one of the most feared clinical signs in horse husbandry and the consequences that can arise from digestive disturbances can be devastating.

Horses are classified as non-ruminant herbivores. The stomach and small intestine are comparable to any monogastric’s digestive tract, but their well-developed hindgut, which harbours billions of microbes, could be compared to a cow’s rumen in terms of fermentative capacity.

The horse’s digestive microflora is rich, complex and plays an essential role in the animal’s health and digestion. The bacteria, yeasts, fungi and protozoa housed within the hindgut assist in the fermentation of fibre, as well as the synthesis of protein and B vitamins. Up to 75% of the total energy produced from a forage-based diet is generated from microbial fermentation – so it is very important to maintain suitable environment for these microbes.

The hindgut provides an ideal environment for microbial development – long transit time and an appropriate and stable temperature and pH. However, these microbes are in a delicate balance and there are several nutritional and stress factors that can disrupt this fragile ecosystem. These include:

  • Composition of diet
  • Meal size
  • Time of feeding
  • Environmental stress
  • Transportation
  • Drug treatments (e.g. wormers, antibiotics)

Domestication and the Advent of Digestive Disturbances

Wild horses in their natural state are characterised by:

  • The need of social interactions: horses are social animals and need to be kept in groups where they can interact with their peers.
  • A forage-based diet: horses are “grazers” that spend most the day (up to 20 hours per day!) feeding on a “little-and-often” basis. Their diet of forage remains consistent, with very little diversification, and provides adequate energy intake. This natural feeding regime is very sympathetic to the structure of the horse’s digestive tract.
  • The need for space and exercise: a horse in the wild naturally received lots of exercise and would cover between 30 and 50km per day.

Domestication has created a very different lifestyle for the horse and humans have had a significant impact in terms of how we feed, house, exercise and manage our horses. Domestic horses are often separated from their peers, confined to stables for long periods of time and have limited access to open space and grazing. Sport horses are subject to intensive exercise regimes and regular transport for competition or racing.

Equine diets have also changed and focus more on concentrate feeds with limited forage intake. Moreover, we tend to feed horses like we feed ourselves – typically two meals a day. Meal feeding does not suit the horse’s digestive tract, with its relatively small stomach that is designed for trickle feeding. Large meals result in food leaving the stomach and passing through the small intestine more rapidly, which reduces the efficiency of digestion and increases the likelihood of undigested starch reaching the hindgut.

Steps involved in the onset of laminitis and hindgut acidosis

(Image used with permission from Lallemand Animal Nutrition)

Why Feed Yeast to Horses?

Several strategies have been developed to prevent microbial disturbances in the equine intestine. One strategy consists of supplementing the diet with probiotics, such as live yeast.

Yeasts are man’s oldest industrial microorganisms: ancient Egyptians used yeast and the process of fermentation to produce alcoholic beverages and to leaven bread over 5,000 years ago. Today, the benefits of yeast in animal nutrition and health are becoming well recognised. Over the past few years, you may have come across Saccharomyces cerevisiae in equine digestive health products, which is the most commonly used yeast species.

Yeast Strain and Live vs. Dead Yeast – Does it make a difference?

To put it simply – yes! Each individual yeast strain has a specific genetic make-up and its own characteristics. Yeast companies profile and select strains based on their function and the specific outcome that is desired. The yeast strain Saccharomyces cerevisiae CNCM l-1077 (under trade name Levucell® SC) has been specifically selected by Lallemand Animal Nutrition through DNA fingerprinting technology for its beneficial interactions with digestive microflora. The natural yeast SC l-1077 is particularly rich in raw fibre-fermenting bacteria and is therefore beneficial for the digestion of raw fibre in the hindgut. Several published trials indicate that it represents a safe and natural solution to enhance and optimise the digestive process of horses, resulting in visible benefits.

Live Yeast vs. Dead Yeast

Live Yeast

Levucell SC10 ME Titan

Yeast culture/Dead yeast
Potency 10 billion CFU/gram Not declared (50-300g/day)
Quality Assessment Active Live Metabolic Cells Vitamins / Amino Acids / Metabolites(?)
Declared on C of A Minimum CFU / gram approved No link to level – only DM, CP, % Moisture
Summary Pure product with a known metabolic / cellular activity


No link between information on C of A and the products use in the field to ensure viability to the animal.


(Table used with permission from Lallemand Animal Nutrition) 

Live Yeast Sc l-1077 Mechanisms of Action

Based on extensive literature available on modes of action of Sc l-1077 in ruminants and its observed benefits in equine, we can link these benefits to two major functions of this specific yeast strain:

  • Its ability to enhance fibre degradation, due to a positive interaction with the digestive fibrolytic microorganisms, bacteria and fungi.
  • Its ability to control pH in the digestive tract, which is also thanks to its interaction with the endogenous microflora.

Improves Feed Utilisation

Sc l-1077 helps to maintain a suitable environment in the hindgut to support a healthy balance of microflora and boost the level of friendly anaerobic bacteria present.

  • Metabolites such as amino acids and B vitamins produced by live Sc l-1077 provides some of the nutrients essential for the development of a healthy balance of microflora.
  • Live Sc l-1077 creates optimal anaerobic conditions for microflora by scavenging residual oxygen in the digestive tract (fibre-digesting bacteria are particularly sensitive to the presence of oxygen).
  • By competing for sugars and other nutrients with undesired, lactate-producing bacteria, Sc l-1077 control their growth.

Stabilises Hindgut pH

Accumulation of lactate and a parallel fall in pH in the hindgut is characteristically seen in horses fed high starch diets, especially where the level of forage is sub-optimal. This change can unbalance microflora and significantly increase the risk of colic and other digestive disorders.

  • Sc l-1077 supplementation significantly increase the number of lactate-utilising bacteria and reduces the total lactate in the hindgut.
  • The stabilisation of the hindgut is seen in the consistency of the droppings in horses fed Sc l-1077.

Mechanisms of action of Sc l-1077 on digestive microflora

(Image used with permission from Lallemand Animal Nutrition)

Improves growth and development of foals

Foals have a high nutritional requirement and have a greater need for quality and digestible protein.

  • Sc l-1077 supports growth through increasing the fermentation of fibre and the absorption of key minerals calcium and phosphorus need to build strong health bones.

Food for Thought

Domestication of the horse has led to significant changes in a horse’s lifestyle that are not compliant with the horse’s natural feeding behaviour and physiology. As a result, the horse is predisposed to digestive disturbances that can have a negative impact on their health and well-being. Clinical case studies and published data indicate that selected live yeast strain Saccharomyces cerevisiae CNCM l-1077 can contribute to improve horse digestion. Supplementation with Sc l-1077 can help to counteract the effects of modern training and feeding practices through stabilisation of equine gut microflora and environment and optimisation of feed digestibility.