First, it’s important to understand that horses need inflammation.
Inflammation is a natural biological response of the immune system to injury, infection, toxins, or damaged cells. It helps the body remove harmful stimuli and initiates the healing process.
Without inflammation, wounds would not heal, infections would not be controlled, and tissue repair could not occur. Inflammation is therefore an essential defence mechanism and a vital part of maintaining health.
The goal is not to eliminate inflammation completely, but to support a healthy inflammatory response and prevent excessive or chronic inflammation that can negatively affect health and performance.
While certain ingredients and feeding practices may influence inflammation, it is important to view the diet and the horse as a whole. Health status, workload, management, and overall nutrition all contribute to a horse’s inflammatory response. Focusing on the bigger picture, often rather than a single ingredient, provides a more accurate assessment of inflammatory status.
Certain factors can contribute to inflammation;
Hindgut disturbances causing dysbiosis. Dysbiosis refers to an imbalance in the intestinal microbiota that disrupts the normal health and function of the gastrointestinal tract.
Why is this a problem in horses?
The equine gut microbiome is an incredibly complex ecosystem containing trillions of bacteria, fungi, yeasts, and other microorganisms. These microbes play a critical role in:
- Digesting fibre and producing energy
- Supporting immune function
- Producing vitamins and other beneficial compounds
- Influencing metabolic processes
- Contributing to the gut-brain axis, which can affect behaviour and wellbeing
Microbes ferment fibre in the hindgut, producing volatile fatty acids (VFAs), which provide a major source of energy for the horse. In a healthy gut, this fermentation process occurs slowly and steadily, allowing acids to be absorbed as they are produced and maintaining a relatively stable pH.
The intestinal lining also acts as an important barrier, allowing nutrients to be absorbed while preventing harmful toxins and microbes from entering the bloodstream.
What happens when dysbiosis occurs?
The gut microbiome is highly sensitive to changes in diet, management, environment, illness, and stress. When the microbial population becomes imbalanced, fermentation patterns can be disrupted.
Put simply, if the microbes are unhealthy or present in the wrong proportions, the horse cannot utilise its feed as efficiently.
A reduction in beneficial fibre-fermenting bacteria and an increase in starch- and sugar-fermenting bacteria can result in excessive production of lactic acid. This can lower hindgut pH and contribute to a condition known as hindgut acidosis.
An acidic hindgut environment can damage the intestinal lining, causing inflammation and erosion of the cells that form the gut barrier. As this barrier becomes compromised, the tight junctions between intestinal cells may become more permeable, allowing toxins and bacterial by-products to enter the bloodstream. This increased intestinal permeability is commonly referred to as “leaky gut”.
Potential consequences of dysbiosis
The effects of dysbiosis can be far-reaching and may include:
- Weight loss or poor condition
- Reduced feed efficiency
- Diarrhoea
- Colic
- Behavioural changes
- Free faecal water (FFW)
- Reduced performance
- Increased inflammation
- Impaired immune function
- Recurring infections
- Increased risk of laminitis
Because the gut microbiome influences so many aspects of health, maintaining a healthy hindgut should be a key consideration in every horse’s nutrition and management programme.
Hindgut disturbances are commonly associated with abrupt dietary changes and excessive starch intake, both of which can disrupt the gut microbiome and trigger inflammatory responses.
How to feed
To support hindgut health, dietary starch levels should be kept within amounts that can be effectively digested in the foregut, minimising starch overflow into the hindgut where it can lower pH and contribute to hindgut acidosis.
In New Zealand, excessive starch intake can originate not only from grain-based feeds but also from lush pasture. When starch escapes digestion in the small intestine and enters the hindgut, it is rapidly fermented by starch-utilising bacteria, leading to the accumulation of lactic acid and a decline in hindgut pH.
If grains are fed, intake should be carefully managed. Research suggests that starch intake should not exceed approximately 1 g of starch per kg of body weight per meal to minimise the risk of digestive disturbances. As a general guideline, grain meals should not exceed 500 g per 100 kg of body weight per feeding.
Horses with metabolic disorders, such as Equine Metabolic Syndrome (EMS) or PPID-associated insulin dysregulation, should be fed diets containing less than 12% non-structural carbohydrates (NSC -including starch and sugars).
Because grains are naturally high in starch (for example, whole oats contain approximately 40% starch on a dry matter basis), processed grains such as extruded or micronized products are generally preferred. These processing methods improve starch digestibility in the small intestine, reducing the amount that reaches the hindgut.
Similarly, access to high-starch or high-sugar pasture may need to be restricted in susceptible horses to help maintain a healthy hindgut environment and reduce the risk of dysbiosis, acidosis, and associated health complications.
Good fibre is KEY
Always provide horses with a diet rich in high-quality fibre from a variety of sources. Fibre is fermented by hindgut microbes, producing nutrients that help fuel the horse’s body and support immune function. Offering a range of fibre sources also promotes a diverse and healthy microbial population within the digestive tract, keeping the PH level stable.
Management and handling practices that keep stress to a minimum are hugely helpful. Just as if you are anxious your stomach is upset, so too is a horse’s stomach!
Omega Fatty Acids
Dietary fats can influence inflammatory processes within the horse’s body, particularly when there is an imbalance between omega-6 and omega-3 fatty acids.
Diets containing large amounts of omega-6-rich ingredients, such as corn oil, rapeseed oil, sunflower oil, soybean oil, and high levels of cereal grains, may contribute to an unfavourable omega fatty acid profile when not balanced with adequate sources of omega-3s. This can result in a diet that is excessively high in omega-6 fatty acids and relatively low in omega-3 fatty acids.
While omega-6 fatty acids are essential and play important roles in normal physiological function, excessive omega-6 intake relative to omega-3 intake may promote a more pro-inflammatory environment within the body. In contrast, omega-3 fatty acids are generally associated with supporting the regulation and resolution of inflammation.
It is therefore important to consider the horse’s entire diet rather than focusing on individual ingredients. The goal is not to eliminate omega-6 fatty acids, but to achieve a more appropriate balance between omega-6 and omega-3 fatty acids. This can be supported by including quality omega-3 sources
Marine sources of omega 3 are far more bioavailable than plant sources. As these sources contain EPD and DHA this is able to be taken up directly from the horse hind gut and used.
Compare this is plant sources such as flaxseed; known for its high amount of ALA (alpha-linolenic acid), which is a short-chain omega-3 fatty acid that must be converted to DHA and EPA within the gut. With the conversion rate being as little as 4% – 10%!
Beware – Fat Oxidation and Rancidity
Fats rich in unsaturated fatty acids, such as most vegetable oils, are highly susceptible to oxidation. As fats oxidize, they become rancid, reducing their nutritional value and producing compounds that may negatively affect your horse’s health.
Oxidation – Oxygen, heat, and light break down unsaturated fats, reducing feed quality and producing harmful compounds.
Unstabilized ingredients – Raw rice bran and ground flaxseed can become rancid quickly due to naturally occurring enzymes.
Low antioxidant protection – As fats in a feed oxidize, the Vitamin E is depleted, making feeds with low antioxidant levels more susceptible to rancidity.
To prevent this, buy feeds that are heat stabilized, contain antioxidant such as Vitamin E, if you are buying an oil make sure it is in a light proof container and store in a cool, dry, dark place in the stable to prevent light sunlight and oxygen from getting in.
Obesity has a role in inflammation
Excess body fat is associated with chronic, low-grade inflammation. Maintaining horses in a moderate body condition can help support overall health and reduce inflammatory stress.
Regularly body condition score your horse (which is a measure of fat pads in horses), alerting you quickly to overfeeding so that you can review feeding.
Conclusion
While inflammation is a normal part of the body’s defence and repair processes, excessive or chronic inflammation can negatively impact health and performance.
By prioritizing digestive health, feeding a balanced diet, maintaining an appropriate body condition, and avoiding practices that disrupt the gut microbiome, horse owners can help support a healthy inflammatory response and overall wellbeing
