The microbiome in the horse’s digestive tract is a living entity of itself, almost like a separate organ system within the body. In states of health, the balance between species of bacteria, protozoa, and yeast is in harmony, while in states of disease, the opposite is true. This state of dysbiosis or imbalance is important and is becoming more closely linked with a variety of health issues impacting the horse based on our research, mirroring what is being revealed in human health. Establishing means of intervention is paramount due to the fact that the problem is becoming more prominent. Our recent research has opened the door for newer options that may be extremely promising not just for gastrointestinal health, but overall health and even soundness in the horse. The results are just incredible!
The influence of the microbiome, or population of bacteria within the digestive tract of the horse, has been an area of heavy interest and research for myself over the past 3 years. This concept has been discussed in many of our other articles regarding horse health and soundness. The most recent is the part one version of this article, where I discussed the underlying problem and potential links.
Prior research in horses has indicated that in many clinical conditions, namely laminitis and metabolic syndrome, there is an evident shift in bacteria species present within the digestive tract. In several studies, one area of concern was the overgrowth of lactic acid bacteria (LAB), which can then negatively influence digestion, inflammation, and overall health of the horse. The exact causes of this overgrowth are unknown, but stress and the diet play a major role. The problem is evident and the connection has been made with potentially many health ailments in the horse, but the solution has escaped us over the past few decades.
This overgrowth of more harmful bacteria is NOT an infection, but a result of a changing environment within the digestive tract of the horse. The harmful bacterial populations are naturally present, but in low numbers, not high enough to cause harm to the host. In order for the populations to shift, something has to trigger one population to die off and another to rapidly multiply. The solution is not an antibiotic nor is it a probiotic, as this would impact the already fragile healthy bacterial population and considering the hostile environment, the probiotic bacteria would likely not survive and thrive. There are so many factors involved with the change in environment that it can be a real challenge in some to stabilize. These factors were originally discussed in the first part of this article.
Looking At The General Horse Population
One thing is for certain and that is that most laminitic and metabolic equine patients have a disturbance or imbalance in their gastrointestinal bacteria, termed a microbiome dysbiosis. In our past research, not only have we noted an increase in lactic acid bacteria in these groups, but other groups of bacteria, including Coliform bacteria, likewise seem to be altered. It is not just one group, but likely several that are negatively altered on some level. The big picture is that more harmful bacteria that are normally present within the digestive tract are increasing in number, while more beneficial bacteria are often decreasing. This is the imbalance and where problems arise.
Over the past 3 years, we have cultured the feces of over 300 horses of all breeds, genders, and disciplines. Some are worked, some are sedentary. Some are on processed food diets, while others are on whole-food regimens. Some receive synthetic based supplements for nutrition or otherwise, while others receive none or herbal based products. Some are on probiotics, while others are not. The end result of these cultures is that the dysbiosis problem is more prominent than we realize.
There are many factors involved with the condition of gastrointestinal dysbiosis, so it is hard to pinpoint one exact cause or connection. Given this, it can be really difficult to find a remedy. The problem exists, but likely the solution for one horse may not benefit another. We discussed the many contributors in Part One of this article.
What is evident is that two factors dramatically play a definitive role:
- Stress (Emotional or Physical)
- Diet (Processed foods vs whole-food)
Even with these two factors, both do not necessarily play a role in any given equine patient. Meaning, we may have a high level of dysbiosis in a horse and believe the diet is a contributor, but after elimination and reculturing, there is no improvement. However, modification of stress levels and the hormonal response in that horse may produce a dramatic response.
The other factor to keep in mind is that as the longer the imbalance or dysbiosis exists, the more damage that is done to the gastrointestinal tract. That damage may be obvious and include ulcers and even bleeding, but in others it is more subtle and on the microscopic level. These changes include localized inflammation of the intestinal lining and increased permeability. One can often alter the microflora and attempt to shift it in a positive direction, but results are often reduced due to the failure to address the damage that is present. If we want to make a real impact, we address both factors.
In a herd setting, we may have 6 horses that culture out on all different levels, despite same genetics, feeding and housing arrangements. Out of that group of 6 horses, we may have 2 that culture out really high, 3 that are midrange, and one that is completely normal. Ironically, the completely normal horse has no health or lameness issues, while the other 5 have some sort of problem whether if it is lameness, weight loss issues, or skin related allergies.
Out of 300 horses cultured in our laboratory, 80% of them demonstrate active dysbiosis with overgrowth of lactic acid bacteria. That is regardless of whether if they were on a probiotic, processed food, whole-food, or otherwise. That is quite incredible and the imbalance that is seen in laminitic and metabolic patients is actually present in a large percentage of horses, with or without active disease, or so we think. In many, this also equates to an overgrowth of Coliform bacteria, which includes E. coli. When this group is overgrown, often we also see an increase in number of pathogenic bacteria types including Salmonella and Clostridial organisms. This may also include Neorickettsia risticii, which is an organism linked back to Potomac Horse Fever in the horse. Taking this all into consideration, it helps us to see why some horses are more prone to developing diarrhea type of conditions and even endotoxemia.
What Does All Of This Mean?
The dysbiosis or shift in bacterial populations within the gastrointestinal tract of the horse can impact almost every facet of health from digestion to joint function. As the population shifts negatively, meaning that more harmful bacteria are present in higher numbers, digestion is impaired, harmful by-products of metabolism are produced, inflammation is increased, and immune function is impaired. This means that joints are impacted, stamina reduced, tendons and muscles are not as strong, hooves do not grow well, overall inflammation is increased, pain levels altered, and in many, sugar and insulin activity impaired.
This is obvious in a case of Salmonella or Potomac Horse Fever, where the dysbiosis has increased the levels of harmful, pathogenic bacteria. However, the impact of the dysbiosis may be on a lower level due to a lower level of harmful bacteria rise. In these cases, the dysbiosis can be directly involved with allergies, eye problems, breathing conditions, tendon health, hoof health, and even joint function. It can also be directly involved with stamina and performance. In horses with higher lactic acid bacterial counts, there is also often a rise in lactic acid production within the body, which can directly impact performance and recovery.
In reality, the problem is increasingly present even in the average horse that may present with no significant medical or lameness concerns. So…is it really a concern?
Case Studies In Equine Gut Health Research
A 7 y.o. OTTB is presented for rehabilitation directly off of the race track. This gelding has had numerous starts and little success due to ongoing lameness associated with foot soreness in both fores. In addition, he has a chronic injury to the right front superficial flexor tendon.
On examination, he is shod with typical long toe, underrun heel presentation. He is sensitive to the sole with hoof testers, with an estimated sole thickness of 4 mm. He is also tender on palpation to the distal superficial flexor tendon on the right front with obvious chronic swelling and edema present. Overall he is a grade 4 lame on lunge and also upon walking on gravel, post shoe removal.
All prior therapies, including special shoes and hoof supplements have failed to provide results for this horse. Upon arriving into our facility, his diet is changed and he is placed on Cur-OST anti-inflammatory supplements, along with a clean diet, alfalfa based, and a barefoot trim. He makes strides over the following 3 weeks, but continues to be tender in the feet.
A fecal culture was performed and indicated a very high level of lactic acid bacteria and numerous colonies of Coliforms. The changes to his diet and environment have made a dent in his soundness, but are not enough as the microbiome is still shifted to the negative.
A new approach was made using a research formula based on concentrated plant polyphenols and other bioactives, along with a patented active form of yeast (Saccharomyces cerevesiae). In addition, he was placed on a new research blend to impact the stress pathways in the horse.
In 5 days, this horse went from a grade 4 lameness to a grade 1. His foot soreness completely reduced and his tendon pain was almost undetectable on palpation. On repeat culture of the feces, the lactic acid bacteria count had reduced by 80% and the Coliform count by almost 75%.
A 6 y.o. OTTB gelding was presented for very similar problems as the first case, sore feet and chronic superficial tendonitis of the right front. The difference was that this horse had been continually shod with the foot protected on a higher level with silicon and full pads, due to unrelentless foot pain. This gelding was also thinner, more internally stressed and less social. He was also a grade 5 lame on lunge and could barely walk on gravel, unless forced.
He was placed on a similar diet and regimen as the first horse, using whole food therapy and Cur-OST anti-inflammatory approach. He responded well in the first 4 weeks, but further progress was stagnant.
On fecal culture, this gelding also demonstrated a very high level of lactic acid bacteria and coliform bacteria, despite the changes in diet and supplementation. Progress was made clinically, but internally, this horse was still impacted.
This gelding was placed on a similar regimen, using the research based concentrated plant polyphenols and other bioactives, along with a patented yeast product. He was also placed on a research blend to alter and mitigate the internal stress response.
After 5 days, he was markedly improved and given a grade 3 lameness on lunge and now was willing to walk on gravel, still with sensitivity present. After 7 days, he was willing to walk completely on gravel with slight sensitivity and now willing to freely lunge. It was also noted that his chronic increased digital pulse that was present in the right front was now almost completely undetectable.
A 27 y.o. Paso Fino gelding was presented for evaluation of poor body condition, despite a good diet, adequate deworming, and inconclusive blood work. His attitude was mildly depressed, but his appetite was good. The feces produced by this gelding varied from normal fecal ball consistency to cow patty.
On fecal culture, this gelding demonstrated very high levels of lactic acid bacteria and coliforms. He was placed on the research formula of concentrated plant polyphenols once daily for 7 days. Upon repeat fecal culture, his lactic acid bacteria and coliform counts were reduced by 50%. His demeanor was improved, more alert and less sluggish. He was also more active in his eating habits and had gained 15 lbs of body weight. His owner had not noted any recent cow patty stools.
An 18 y.o Paint mare was presented for evaluation of chronic laminitis. She was on a processed diet along with roughage and confined to a dry lot for the past 4 years. This mare was a grade 5 lame upon presentation with full shoes and pads applied.
As part of her initial therapy, her shoes were removed and her feet trimmed every 2 weeks. She was placed on a clean diet of whole oats and alfalfa pellets, along with alfalfa hay. Her fecal cultures indicated high levels of lactic acid bacteria and coliforms.
She was placed on a modified version of the research formula based on concentrated plant polyphenols, with added Curcumin to aid in further modification of inflammation. Curcumin or Turmeric can also be helpful in some to aid in further repair of tight cell junction leaks, which lead to increased permeability of the intestinal tract.
In 2 weeks, the mare went from a grade 5 lame to a grade 3. In the following 4 weeks, she further reduced to a grade 2 lame and was willing to be lunged for the first time in years. Upon reculturing of her feces, the lactic acid and coliform bacterial counts had reduced dramatically. Changes in her hoof growth as a result can be seen in the images below.
The Bottom Line with Dysbiosis
For many centuries, natural physicians around the world have made the claim that health begins in the digestive tract. As we evolve with research, this is becoming ever more evident as we begin to notice bacterial populations that are out of balance in the horse. These states of dysbiosis can impact every facet of health and soundness. Inflammation levels in the patient often rise with the level of dysbiosis. If we balance out the dysbiosis and inflammatory levels drop. This inflammation impacts every facet of horse health and soundness.
The horse with obvious diarrhea, loose stools, ongoing colic, or even gastric ulcers is a prime example of the impact of a dysbiosis. But, seeing how this problem is present in a large portion of horses researched, it raises the concern of how deeply it is involved with tendon injuries, joint concerns, hoof health, allergies, performance and stamina. Is it also connected back to emotional issues such as anxiety and stress?
The answer to all of this is…yes. They are intertwined. The new approach may be to target the bacterial population within the gut, aiming for rebalance, which may then dramatically impact many concerns. Instead of using probiotics, medications, special shoes, and believing certain ailments are linked to vitamin or mineral deficiencies, maybe we should be putting our sights on the gut. Instead of using a probiotic to ‘boost’ health bacteria, maybe we should be targeting overall balance and reduction of the more harmful bacteria. After all, if the harmful bacteria are more prominent in numbers, then the gut environment has changed and more toxic, which would impede any beneficial bacterial growth, including a probiotic. We have to impact the harmful overgrowth and change the environment. If we can do this successfully, the beneficial bacteria will increase in numbers by themselves, with no or little probiotic intervention. As we achieve balance in this organ system, inflammatory parameters are more manageable and digestion is enhanced.
In the past with horses, we have targeted the gut with several of our current Cur-OST® formulas and in many cases, the horses biomes respond favorably. Two popular formulas that aid in this aspect are the Cur-OST EQ Total Support and Cur-OST EQ Stomach. Both of these blends have aided to rebalance the microbiome in many horses, resulting in clinical improvement. However, there are many horses that are more critical and damaged internally, that fail to fully respond.
As of right now, I am extremely impressed with this new approach and regimen. It is rathers simple and effective. The dramatic change in the patient attitude and level of soundness is huge not only in hoof health, but tendon strength. In only 5 days, there was marked improvement and changes on repeat fecal cultures. Pretty impressive to say the least. That is the power of the body to heal, when all factors are put into balance. I realize that this is only one approach to a difficult situation, but overall it does show the capabilities of modifying the gastrointestinal microbiome. Through this modification, negative factors impacting the body and health can be reduced, and thus, the pathway to healing put into force.
We are continuing to research this approach with many horses and hope to be able to provide this as an option for future patient care. If you are curious as to how your stacks up with others and whether if an overgrowth may be a problem, check out our Equine Fecal Culture page, where you can order up a test and gain information on how to submit a sample!
Author: Tom Schell, D.V.M, CVCH, CHN