A horse’s digestive system is a finely tuned machine designed to process a steady intake of forage and fibrous plant material. This fibre is broken down through fermentation by billions of microbes living in the hindgut. These microbes play a crucial role in digestion, nutrient absorption, and overall health.
If you want to optimise your horse’s nutrition, prevent digestive disorders, and ensure peak performance, understanding the hindgut microbiome is key. In this blog, Lisa Elliott MSc – Equine Nutrition Solutions, explains the equine hindgut, the role of microbes, and how proper feeding supports a healthy digestive system.
The Equine Hindgut: A Fibre-Fermenting Powerhouse
The hindgut consists of the caecum, large colon, small colon, and rectum—together forming the ‘large intestine.’ The size of this system highlights just how important fibre is in a horse’s diet:
- Caecum: 1.2m long, holding 28-36 litres
- Colon: 3-3.5m long, holding 86 litres
- Total Hindgut: Makes up 60% of the digestive system
Horses cannot digest fibre on their own—they lack the necessary enzymes. Instead, microbes within the hindgut ferment the fibre, producing energy-rich compounds called volatile fatty acids (VFAs)—acetate, propionate, and butyrate. This fermentation process requires a stable environment, with an optimal pH of 6.5 – 7.
How Microbes Support Digestion and Health
The hindgut microbiome is made up of bacteria, protozoa, fungi, archaea, and viruses, all working together to maintain digestion and overall health. Here’s what they do.
1. Fibre Fermentation
Cellulolytic (fibre-digesting) bacteria break down plant fibres, producing VFAs, which provide a major energy source for your horse.
2. Protein and Nitrogen Metabolism
Microbes help break down and synthesise protein, influencing amino acid availability. However, most of these amino acids benefit the microbes themselves rather than the horse.
3. Vitamin Production
Microbes produce essential B vitamins (including Biotin) and vitamin K, which support hoof health, energy metabolism, and blood clotting.
4. Gut Health and Immunity
- Microbes strengthen the gut lining and immune system, reducing disease risk.
- They prevent harmful bacteria from taking over—a protective function called the ‘barrier effect.’
- VFAs, particularly butyrate, stimulate gut cell growth, helping to maintain intestinal integrity.
How Diet Affects the Hindgut Microbiome
The horse’s diet is the biggest factor influencing the health and balance of the hindgut microbiome.
Forage First: Horses are designed to consume a high-fibre diet of grass and hay. A steady supply of fibre maintains a healthy, diverse microbiome.
Avoid High-Starch Diets: Feeding large amounts of cereals or processed feeds can upset the balance of microbes. Undigested starch that reaches the hindgut is rapidly fermented, producing lactic acid and lowering pH levels. This can lead to hindgut acidosis, causing colic, laminitis, and behavioural changes.
Sudden Diet Changes: A rapid change in diet can disrupt microbial populations, leading to digestive upset like diarrhoea or colic. Always transition to new feeds gradually over 7-14 days to allow microbes time to adjust.
What Happens When the Hindgut Microbiome Is Unbalanced?
Hindgut dysbiosis occurs when microbial balance is disrupted—often due to high-starch diets, stress, or antibiotics. The consequences may include:
- Colic: Gas build-up, impaction, or motility issues
- Laminitis: Excess lactic acid and endotoxins trigger systemic inflammation
- Poor Nutrient Absorption: Reduced fibre fermentation and VFA production lower energy levels
- Weakened Immunity: An imbalanced microbiome can increase infection risk
How to Support a Healthy Hindgut Microbiome
Keeping your horse’s digestive system healthy means maintaining a balanced, fibre-rich diet. Here’s 7 things to do to help your horse.
- Prioritise Forage
Provide unlimited access to high-quality hay, haylage, or grass to support microbial stability and effective fibre fermentation. - Encourage Diet Diversity
A diverse diet promotes a diverse microbiome, reducing the risk of digestive upset. Coligone Fibre Cubes can be fed alongside forage to increase fibre variety and support hindgut health. - Limit Starch Intake
Reduce cereal-based feeds and opt for fibre-rich alternatives like Coligone Fibre Cubes and Coligone Fibre Bio. Keeping starch levels low helps maintain a stable microbial environment. - Introduce New Feeds Gradually
Allow 7-14 days (ideally 2-3 weeks) for dietary transitions to prevent digestive upset. - Use Prebiotics and Probiotics
Supporting beneficial microbes is essential. The Coligone range includes Yea-sacc (probiotic) and scFOS & MOS (prebiotics)—scientifically proven to stabilise the hindgut microbiome. - Minimise Stress
Transport, competition, and sudden environmental changes can disrupt gut microbes. Where possible, reduce stress factors to support gut stability. - Provide Clean Water & Electrolytes
Hydration is crucial for microbial function. Providing access to a salt lick helps maintain daily salt intake, promoting fluid balance and digestive health.
By focusing on providing your horse with a fibre-rich, well-balanced diet, you can help your horse maintain a healthy hindgut microbiome, reducing the risk of digestive issues while supporting overall well-being and performance.
