The equine digestive or gastrointestinal microbiome is a vast organ system within an organ system, that can greatly impact horse health and soundness.  It is a complex system of hundreds of different microorganisms that not only impact digestion, but overall health and inflammation within the horse. When this system is out of balance, a dysbiosis exists.  Correcting this imbalance or dysbiosis is the first step with any horse’s recovery, no matter what issues are at hand.  The steps to promoting balance are simple, but often interlinked, so there is no one easy solution.

The process of digestion, gut health, and the microbiome in the horse was discussed in a prior article. The problem was revealed and discussed in more detail, announcing that the issue exists, but the question is now what are you going to do about it?

Bacteria and the Equine Digestive Microbiome

Bacteria and the Equine Digestive Microbiome

In my clinical patients, I tend to perform fecal cultures to assess the degree of overgrowth, and thus, the degree of perceived dysbiosis.  This is often my first step, but in many patients, this step is not always needed, as prior experience will simply tell us that the problem is present and impacting their health on some level.  The reality is, at least in my research and practice, that upwards of 80% of all horses with chronic inflammatory conditions demonstrate an overgrowth or dysbiosis on fecal cultures.  This is a pretty big number and when we look at human research data, the dysbiosis that is noted could be the key instigator in many health problems in the horse.

So, how do we ‘fix’ this dysbiosis or microbiome imbalance?

Restoring Balance to the Equine Digestive Microbiome.

The digestive microbiome in the horse is a complex inter-relationship of hundreds of bacteria, yeast, and protozoal organisms.  There are different species of these organisms in different levels throughout the digestive tract, so things can and will change dependent on where you are looking. When there is a dysbiosis or imbalance, it is not about one single organism, but more often it is about large populations that have either increased or decreased in number.  In cases of Salmonella colitis or Clostridiosis, both of which can cause diarrhea in the horse, you may think it is just the Salmonella or Clostridial organism that is the culprit, but in reality, there is an entire shift.  The changes to the microbiome creates changes in the digestive tract which impacts other populations.  In the case of Salmonella, as an example, this organism is normally present in very low levels in the healthy horse, but when a dysbiosis develops, this harmful bacteria can multiple in numbers and create disease.  Even in those cases, we can use targeted therapies against Salmonella, but in order to truly regain health, the entire microbiome must be addressed.

When it comes to the microbiome and digestive health in the horse, I look at 4 key factors:

  1. Diet that is being fed, including grains and roughage
  2. Stress (emotional or physical)
  3. Inflammatory status of the patient
  4. Medications currently being administered

Fixing the microbiome is not about using a targeted therapy, such as an antibiotic or even a probiotic.  These therapeutic tools may be helpful in acute infectious cases, but in the long term can create more imbalance, which then further impairs health for the horse.  In order to fix the microbiome, you must promote balance between the populations of organisms.  Create the right environment, and the organisms will regain balance naturally to the highest extent possible.

It is all about creating and fostering the healthy gastrointestinal environment.  Just like with a plant, the environment must be right to grow which includes healthy soil, nutrient provision, water, and sunlight. The digestive microbiome is not much different in the horse.  Feed and support it properly, and it will flourish.  But, it is not just about the food.

The Diet and Impact on the Digestive Microbiome in the Horse

What you put into your horse’s body in terms of food, dictates how healthy your horse is and also the health of their microbiome.  Looking at human research data, one of the biggest contributors to a dysbiosis and ill-health in people is their diet.  Meat eaters and mostly plant eaters have an entirely different microbiome and the meat-eater microbiome is perceived as being more inflammatory in nature. The consumption of processed foods, in human data, is also tightly connected with the health of the microbiome.  It is not only processed foods, laden with chemicals and synthetic nutrients, but also the lack of proper fiber, that can create bacterial imbalances in the digestive tract.

When I am presented with a horse that has chronic inflammatory conditions, the first question that is often asked is relating to the diet.  What is the owner feeding the horse?  Considering that about 80% of these chronic inflammatory cases have evidence of dysbiosis, I’d guess that 75% of those horses are fed commercial, processed feeds by their owner.  The other 25% are often not fed any grain, but on deeper examination, are fed inferior hay sources or have no access to pasture.

The overall concern here is that the processed, commercial feeds may be contributing to the dysbiosis and thus the inflammatory conditions in the horse.  Most of the time, the owner is seeking a cheap, easy to feed, and ‘supplemented’ feed source to boost their horse’s health.  However, these feed sources are not much different than you and I eating processed foods every day, they will create damage no matter how fortified they may be.  The fact is that these are not real foods.  The dyes, chemicals, preservatives, and unnatural food sources that are often used are not natural to the horse’s digestive tract.  In many cases, these chemicals are rejected during the process of digestion, and with this rejection there is an inflammatory response created within the gut.  Create inflammation, then you change the local environment and can influence the microbiome.

The other issue of concern is the level of natural protein and fiber that is present in the diet, which can be acquired via the grain source or the roughage.  Is there sufficient protein and fiber, and second, is that of a desirable source?  Fiber and protein are both needed to support gastrointestinal health.  Fiber, more importantly, is needed to help build and foster the bacterial growth in the gut.  Soluble fiber is broken down and used as a food source by the bacteria, while insoluble fiber helps to bind water and support healthy bowel motility, which also impacts the microbiome in the horse.  Many horses on commercial feeds or given low quality roughage sources are not receiving adequate levels of these nutrients.

In our patients, the first step is to get on a natural diet, away from commercial feeds.  In those horses, we use whole grains such as oats or sunflower seeds, but in limited volumes.  When fed in high volumes, the carbohydrates from the grains can drift over into the hindgut and alter the microbiome.  This is also a source of problems for many owners, over feeding of grains.  We utilize grains in our program but in limited amounts, often combined with alfalfa or timothy pellets and dried carrots and peas to round things out.  They are not being used as a meal but more often as a healthy snack of sorts, and a medium for supplement administration if needed.

The second step is increasing the forage quality, which usually means an alfalfa hay or alfalfa-mix type, fed at 1.5-2% of BW per day, dependent on the body condition of the horse.  This higher quality hay source will provide a higher nutrient level to the patient and often, a higher level of soluble and insoluble fiber to support the microbiome.  This is fed in addition to quality turnout.

Stress and the Impact on the Digestive Microbiome in the Horse

Stress is something that most horse owners do not equate with being a horse, but the fact is that stress is often a huge factor in their lives.  Any time a horse is experiencing a health or lameness condition, they are experiencing stress on an emotional and physical level.  Then, there is the horse that is under constant training, stall bound, or not exposed to pasture mates.  All stressful situations indeed and this stress response impacts the digestive microbiome in the horse.

Think about the last time you experienced stress.  Now reflect on the impact on your digestion.  In most cases, this stress you felt is equated in an upset stomach, nausea, diarrhea, or constipation.  This is not much different in the horse.  The stress response leads to altered cellular signaling and hormone release. Normal gastrointestinal motility, or movement, is altered.  In some cases, things are sped up which can lead to loose stools. In other cases, things are slowed down, which results in constipation.  In either case, the stress response impacts motility and localized health to the digestive tract.  This then impairs the microbiome and bacterial imbalance.

I assume that stress is present in most of the cases I am consulting on, but how that stress is addressed is patient dependent.  In many, simply altering the environment and letting that horse have more turnout time is sufficient.  In others, there is a needed break from training and competition to ease the stress.  For some horses, these approaches do work and assist us in our goals, but in others there is still an ongoing stress response which may be directly linked to the health condition.  Here, I will often use adaptogen herbs to benefit the stress response, help to rebalance it, and reduce the impact on the horse.

There are many adaptogens that can be used in the horse, but the main ones I tend to focus on include Ashwaghanda, Bacopa, Schisandra, Hawthorne, Cordyceps, and many others.  Each herb can help us to reduce the internal stress response and rebalance the HPA axis in the horse.  If you can alter that stress response, then you are one step closer to achieving balance in the horse.

Chronic Inflammation and Impact on the Digestive Microbiome in the Horse

Inflammation is a fact of life for horses and is the main contributing factor to the aging and health deterioration process.  Inflammation can be created by a dysbiosis in the digestive tract, but it can also create a dysbiosis.  It is a two-way street, working in both directions.  In most of the horses with chronic inflammatory conditions, there is an evident dysbiosis, but the question is who came first?  You may have a horse with laminitis, as an example, with chronic pain and inflammation in the foot, but also has a significant dysbiosis present.  Did the dysbiosis create the foot problems or did the foot problems create the dysbiosis?

It is hard to determine cause and effect in these cases, and honestly, I personally don’t care.  The point is that chronic inflammation is present and likely uncontrolled.  If you want to impact the horse positively, then this needs to be addressed.  However, you need to realize that this chronic inflammation is not just present in the foot, joint, tendon or in the eye of that horse, but is also present in the gut or digestive tract.  In fact, more often than not, this is likely where it all stems from in the average horse.  Just hard to prove scientifically.

In my patients, I tend to manage that inflammatory response through nutrition as outlined above, moving away from the processed foods.  I will also implement specific herbs that are known for their anti-inflammatory properties and also benefit the digestive tract.  If I can impact or lower the inflammatory response in the digestive tract, then the local environment can be stabilized, and the microbiome is then given the opportunity to self-balance.

The main herbs that I use in our patients include:

  • Curcumin (Turmeric)
  • Parsley
  • Dandelion
  • Marshmallow
  • Aloe
  • Terminalia chebula
  • Terminalia bellerica
  • Phyllanthus emblica
  • Humulus lupulus
  • Various mushrooms

These herbs are often used in combination with variable levels of dosing and given once to twice daily, dependent on the patient.  There are several interesting things to note here.  First, these herbs don’t just impact inflammation in the digestive tract, but impact it throughout the body.  So, there is benefit to that aching joint, foot, tendon, or even eye.  Second, many of these herbs have natural anti-microbial properties and research indicates that they help to reduce levels of harmful bacteria in the digestive tract.  So, they are actually helping to directly restore balance to the microbiome.

Medications and Impact on the Microbiome in the Horse

Medications or pharmaceuticals are the next thing on my list.  Many of the horses that I consult with are on a shopping list of medications from non-steroidals to ulcer medications.  Some are also on hormones such as thyroid supplements or progesterone.  I am not against the use of these medications in the short term, acute type of case, but most of these horses have been on these medications as a means to an end, but that end or solution has never appeared.  You have to keep in mind that these medications can and do impact gastrointestinal motility or the microbiome directly.  Ulcer medications, as an example, reduce acid secretion in the stomach, which impacts food digestion.  This then impacts nutrient provision for the patient and may impact the microbiome due to lack of proper fiber availability.

My goal for most of these patients is to get them off of the medications as quick as possible without creating a crisis for the patient.  I realize that some medications have a purpose and will keep that in mind.  However, I also realize that many of the medications are being given to combat a problem that is related to chronic inflammation and poor digestive health in that horse.  If I can manage those issues more readily, then there is little need for those medications in the end.  This is a win-win situation for both owner and horse.  Reduced cost and reduced risk to the horse.

Digestive Health and Overall Health in the Horse

The writing is on the wall, when it comes to human health, research, and the digestive microbiome.  We are what we eat and what we ‘feel’ in regards to our emotions.  This all translates into poor digestive health and increased risk of chronic inflammatory health conditions.  This is the same situation in the horse, but research is just lagging in time proving it.  It is really obvious when you just take time to look. The good news is that if you can recognize it, that is the first step.  The next step is making the necessary changes to promote and regain that digestive health.

If you find yourself battling with ongoing health or lameness conditions in your horse, I encourage you to take a closer look at his digestive health.  If you think that using a simple probiotic or ‘gut’ formula is the key and the solution, you may be misled.  Rebalancing the gut and the microbiome in your horse is a multi-step process, which can take time, but is readily accomplished.  The rewards can be very quick and mind-blowing when realized.


Author:  Tom Schell, D.V.M., CVCH, CHN


Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.