Understanding Inflammation and your Horse | BioStar US

Understanding Inflammation and Your Horse

The inflammatory process is both fascinating and complicated. The essence of inflammation is the normal protective response by the body’s defense system. As with humans, inflammation in horses is an important part of the body’s system of healing and repairing.

The body’s inflammatory response activates when tissues are injured by trauma, toxins, bacteria, heat, and stress. The damaged cells release histamine, bradykinin and prostaglandins. These chemicals cause blood vessels to leak fluid into the tissues, which causes swelling.

Inflammation can occur systemically as well, affecting the whole body.

The three phases of inflammation

Acute: the swelling stage (redness, heat, swelling, pain, loss of function.)
Sub-acute: the regenerative stage
Chronic: persistent, low grade inflammation. Chronic inflammation plays a role in a variety of health issues in horses: metabolic disease, leaky gut, laminitis, musculoskeletal injuries.

The role of the immune system

Inflammation is a vital part of the immune system’s response to injury and infection. When tissues are damaged, the inflammatory response is initiated and the immune system becomes mobilized. Without inflammation as a biological response, wounds would fester and infections become deadly.

The immune system secretes pro-inflammatory cytokines, which are chemical messengers. These messenger proteins are important for the biological response to infections or injury and help the body in the acute and sub-acute regenerative stages.


Pain and inflammation

Following a physical injury, cytokines initiate the healing process and provide a protective pain response. It is important to remember that low-level inflammation associated with tissue repair is not detrimental. Some post-exercise inflammation is normal.

However, elevated or chronic inflammation can cause muscle tissue damage and scarring.

Physical injury combined with chronic stress may result in a constant inflammatory response that impairs healing.

The secondary effects of widespread inflammation can affect autoimmune sensitivities, widespread oxidative and free radical damage, and tissue degeneration.

Inflammation in Horses: How It Happens & What to Do | BioStarUS

Inflammation and the connection with stress

The reaction of the body under stress depends on stress duration, stress intensity, and stress frequency.

Short term, acute stress is an adaptive response. The release of cortisol when the body is under stress helps to promote survival. Cortisol is a potent anti-inflammatory that functions to mobilize glucose reserves for energy and modulate inflammation.

However, prolonged stress or chronic stress can lead to cortisol dysfunction. This can cause widespread inflammation and pain.

Stress can be emotional, psychological, or physical. How a horse experiences stress may not be the same as the horse in the stall beside him. This is true of humans as well. What stresses one
person, may not be the same as her sister, friend, or parent.

Research has indicated that prolonged or constant low-amplitude stress may perpetuate the cycle of inflammation and pain. 1

Inflammation in Horses: How It Happens & What to Do | BioStarUS

Whole body inflammation

Researchers have begun to study whole-body inflammation in horses. There are clear indicators that whole-body inflammation is linked to leaky gut syndrome, musculoskeletal injury, equine metabolic syndrome, insulin resistance, and laminitis.

Whole body inflammation can occur when the body’s protective responses become amplified and chronic. Triggers of whole body inflammation include: stress, obesity, high sugar and starch diets, intense exercise, and NSAIDs.

Leaky gut and inflammation in horses

In horses as in humans, the intestinal tract forms barriers when cells and membranes join together. These are called tight junctions. They form protective and functional barriers. When the tight junctions are disrupted, illness can result from the systemic effects of toxins and pathogens that leak through the intestinal wall. The immune system then reacts with the inflammatory response.

A study in the Journal of Equine Veterinary Science (2017) highlighted the stress-induced barrier dysfunction: “a variety of stressors (physiologic, pharmacological, psychologic, and others) affect the intestinal barrier.”2

Leaky gut has been associated with systemic inflammation, immune system disruption, obesity, poor performance, exercise intolerance, and inflammatory bowel disease.

Anti-Inflammatory drugs (NSAIDs) and their consequences

Some veterinarians point to long-term NSAID use affecting intestinal permeability (leaky gut syndrome). This increases the risk of a systemic inflammatory response.

Because NSAIDs can mask pain, and pain is part of a protective mechanism in the acute phase of inflammation, overuse of NSAIDs can help an injured horse keep working, which can cause more structural damage. Mild and moderate inflammation in the acute stage is actually necessary for the repair process of the regenerative and recovery stage.

According to David Horohov, PhD, chair of the department of veterinary science and director of the University of Kentucky’s Gluck Equine Research Center in Lexington,

Since NSAID administration is thought to lead to ulcer formation, omeprazole, a proton pump inhibitor drug, is frequently given with NSAIDs. However, studies have shown the opposite effect, with proton pump inhibitor drugs actually exacerbating NSAID-induced intestinal damage.3

When the equilibrium is disturbed: oxidative stress

Oxidative stress is a common term regarding performance horses. Oxidative stress is a physical stress, an imbalance between the production of free radicals and their elimination. This imbalance can lead to chronic inflammation. There is evidence that this inflammation which is triggered by excessive oxidative stress may be the cause for several chronic diseases including Insulin Resistance and laminitis.

Factors that contribute to oxidative stress are diet, lifestyle, environmental factors such as pesticides and pollution, as well as intense exercise. It’s not just performance horses who may deal with chronic oxidative stress.

The production of free radicals and oxidants play a dual role as both toxic and beneficial compounds, so they may be harmful, or they may be helpful. When an overload of free radicals cannot be destroyed by the body’s defense mechanisms, their accumulation in the body is called oxidative stress.

Normally, free radicals are produced in the body in a limited quantity and are involved in the regulation of cell homeostasis and activation of receptors. But when the body’s defense systems are overrun by free radicals, the result is oxidative stress.

Free radicals can be produced from external sources such as medication, pollution, industrial chemicals, pesticide exposure or by normal metabolism, intensive exercise, and microbial infections.

Remember, there is a healthy balance between free radical formation and the body’s defense mechanisms. It is when this balance is disturbed that it can lead to widespread inflammation, as well as tissue damage.

Inflammation in Horses: How It Happens & What to Do | BioStarUS

Antioxidants for oxidative stress

When the body is under a lot of stress, the production of free radicals is amplified. Antioxidants help neutralize free radicals to reduce inflammation.

Some helpful antioxidants include:
Zinc, Vitamin E, Resveratrol, Quercetin, Boswellia, Turmeric, and Superoxide Dismutase.4

Resveratrol in Grapes | BioStar US

Food sources of resveratrol include the skin of grapes, blueberries, and raspberries.

Support for the body

  1. Sugars and starches are digested in the small intestine where the tight junctions reside. Even if your horse is not an easy keeper, be mindful of the sugars and starches in your horse’s diet. Equine athletes can utilize higher amounts of simple carbohydrates and sugar, but horses in light to moderate work generally don’t need high levels of sugar and starch.
  2. Get your hay tested so you know how much NSC % is in your hay.
  3. Omega 3 fatty acids are important for the balance of essential fatty acids: the omega 3:6 ratio. Omega 3 fatty acids help regulate inflammation. If your horse doesn’t have access to healthy pasture 6-10 hours per day, you may need to supplement with flax or chia for a healthy omega 3:6 balance.

Support for stress

We cannot address acute inflammation, chronic inflammation, or whole body inflammation without addressing the stress component.

holy basil tulsi - BioStar US

Regulating cortisol with various Ayurvedic plants such as Ashwagandha and Holy Basil can help restore homeostasis.


Red Reishi MushroomSupporting the adrenal gland, from which cortisol is released, can be supported with the medicinal mushrooms: Cordyceps and Reishi.


Health begins in the gut

When assessing a new supplement or feed, always ask yourself: will this decrease stress on the GI tract, or increase stress?

Inflammation is an important biological process that is complicated, fascinating, and sometimes mystifying. Managing stress, medications, and diets high in sugar and starch are paramount to maintaining homeostasis and a healthy immune and inflammatory response.



  1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4263906/#B62
  2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6467570/
  3. https://thehorse.com/161728/its-all-connected-bodywide-inflammation-in-horses/
  4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3614697/


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