Fecal Transplants for Horses: Does Equine Microbiome Therapy Improve Gut Health?

Fecal Microbiota Transplantation (FMT), commonly referred to as “fecal transplants” or “fecal transfer,” is a procedure gaining recognition in equine medicine. This procedure originated in human medicine, but veterinarians and horse owners alike are interested in its potential to support gut health in horses suffering from gastrointestinal disorders like diarrhea.

The process involves transferring fecal material from a healthy donor horse to a recipient horse who has an imbalanced gut microbiome. This method helps reintroduce a balanced microbial community to the digestive tract. The influx of healthy bacteria may out-compete harmful pathogens in the tract, ultimately restoring digestive health.

While FMT has been practiced informally for years, it has gained recent attention due to advancement in human medicine. Researchers are optimistic about its safety and efficacy, but more studies are needed to establish standard protocols and fully understand its long-term benefits for horses.

FMT offers a promising alternative to traditional antimicrobial therapies, which can disrupt gut health and contribute to antimicrobial resistance.

Fecal Transplants for Horses

Fecal microbiota transplantation (FMT) is a technique which involves transferring fecal matter from the gastrointestinal tract of a healthy horse to that of one with some form of digestive disorder. ^{[1][2][2][3][4][5]}

The purpose of fecal transplantation is to reinstate a healthy microbiome in the recipient horse’s gut. ^{[6][7][8][9][10]}

Once transplanted, the micro-organisms from the healthy horse compete with and replace pathogens that are responsible for illness in the recipient, thereby restoring the balance of a healthy gastrointestinal environment. ^[1]

Terminology

To better understand what fecal transplantation is and how it is used, it’s useful for horse owners and caretakers to familiarize themselves with some terms about the procedure and the microbiology involved.

Microbiota

The term microbiota refers to the collective group of individual microorganisms that live in a particular environment. This includes bacteria, fungi, viruses, and protozoa. ^[6]

In discussions about equine FMT, “microbiota” primarily refers to the microorganisms that live in the horse’s digestive tract, but there are also microbiota on the skin and other parts of the body. ^[1]

The term microbiome refers to the entire ecosystem of microorganisms in a particular environment, whereas the microbiota are the microorganisms themselves. ^[1]

Microbes

“Microbes” refers to the individual organisms that populate the microbiota. Some microbes that make up the microbiota promote overall health in the horse. These are known as non-pathogenic microbes. Non-pathogenic microbes have many roles, including modulation of the immune system. ^[9]

Some microbes found in the microbiota are capable of attacking the body, leading to gastrointestinal imbalance and disease. These are known as pathogenic microbes. If pathogenic microbes are not well-controlled by the immune system, they can proliferate, leading to infection, inflammation, and systemic (whole-body) illness.

The horse’s gastrointestinal tract is home to over 1000 species of bacteria as well as many other microorganisms. Without these organisms, it would be impossible for the horse to ferment and digest food and absorb nutrients. ^[1][5][9] They also play a role in many other physiological functions. ^[1]

Horses always have both pathogenic and non-pathogenic microbes in their microbiota. In fact, a diverse and balanced microbiota is considered a sign of a healthy horse. ^[2][5]

Significant alterations to the normal microbiota, especially an imbalance that favors pathogenic microbes, is known as dysbiosis. ^[6][9] During dysbiosis, the horse is at risk of developing a number of gastrointestinal diseases including colitis and symptoms including diarrhea. ^[1]

Donor & Recipient

The donor horse is the horse with the healthy gastrointestinal system from which the fecal matter is collected. ^[1] The recipient horse is the horse with the unhealthy gastrointestinal system who receives the fecal transplant. ^[1]

Fecal Transplant in Equine Medicine

FMT was first used in human medicine as a treatment for Clostridium difficile infections in 2013. ^[1]

Since then, it has gained attention by veterinary researchers as a potential therapy for gastrointestinal disorders in horses. ^[1] While it is still being studied, the complete benefits for our equine companions are not yet fully understood. ^[1]

So far, studies on equine FMT have shown it to be mostly safe and effective for horses with gastrointestinal disorders, including diarrhea or colitis. ^[1] However, the current data is still too limited to draw definitive conclusions about the overall effectiveness or safety of fecal transfer in horses. ^[1]

Anecdotal reports from owners and veterinarians suggest that FMT can be a direct, effective, and economical treatment option in certain cases. ^[1]

Although most of the literature is positive about the efficacy of FMT, some suggest it has limitations. ^[8] Individual susceptibility may be a major component of whether the microbiota of specific horses is affected by this procedure. ^[6] It is also possible that the changes to the recipient horse’s microbiota may be short-lived. ^[6]

Clinical Uses

FMT has been used for several years in equine medicine based on anecdotal reports that it is beneficial for conditions associated with dysbiosis. ^[4][5] FMT is most frequently used for horses with diarrhea related to dysbiosis, but has been used for treatment of other causes of colitis. ^[1][2]

Causes of colitis include: ^[8]

• Salmonella spp. infection
• Clostridioides difficile infection
• Clostridium perfringens infection
• Neorikettsia risticii infection
• Equine coronavirus
• Parasites such as cyathostomins
• Antimicrobial drugs
• Nonsteroidal anti-inflammatory drugs
• Dietary imbalances
• Carbohydrate overload
• Sand impaction
• Inflammatory bowel disease
• Post-operative complication

Unlike other treatments, FMT does not require identifying the specific microbe causing gastrointestinal issues. Instead, it introduces a diverse set of microbes from a healthy donor horse, which may help rebalance the gut environment and potentially out-compete harmful pathogens. ^[3]

FMT has also been tested on horses with free fecal water syndrome – a condition where the consistency of the manure is normal, but water exits the horse’s body during, before, or after defecation. So far, these studies have conflicting results, and it is unclear if FMT is a viable option for these horses. ^[1][10]

Some owners and veterinarians are interested in pursuing FMT as an alternative to antimicrobial drugs including antibiotic, antiviral, and antifungal medications. ^[7]

However, FMT should always be used as part of a comprehensive treatment plan, alongside other therapies, to support overall gut health. Other strategies to restore balance in the gut microbiome without harmful side effects include: ^[9]

• Feeding a forage-based diet with adequate fiber
• Supplementing with probiotics, prebiotics, yeast, and digestive enzymes

Effects on the Digestive System

The exact mechanisms of how FMT works are not yet fully understood. ^[1]

The treatment is based on the idea that non-pathogenic microbes act as a primary defense against harmful pathogens. ^[3] By introducing a diverse and balanced microbial community into an imbalanced gut, FMT may help restore microbial equilibrium more quickly. ^[1]

However, defining what constitutes a “healthy” gut microbiota remains challenging and is not yet fully characterized. ^[1][9] Additionally, variations in gut microbiomes between individual horses add complexity, making it difficult to establish standardized treatment protocols.

Antimicrobial Resistance

Another reason for the growing interest in FMT as a medical treatment is its potential as an alternative to antimicrobial drugs. ^[1] In horses, as in other domestic animals, antimicrobial resistance (AMR) is a significant and ongoing concern. ^[11]

AMR arises from the overuse and misuse of antimicrobials, allowing microorganisms to evolve and resist drugs like antibiotics, antivirals, and antifungals that were previously effective. ^[11]

This resistance can lead to persistent infections, often termed “superbugs,” increasing the risk of disease spread and making infections harder to treat. Since resistant strains can spread rapidly, they pose a serious global health threat, especially when no effective antimicrobials remain. ^[11]

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Fecal Transplant Procedure

A standardized protocol for FMT in horses has yet to be established. Current experimental procedures are largely adapted from those developed for humans, with ongoing research aimed at refining the process to maximize efficacy and minimize potential risks. ^[4]

In general, equine FMT is performed in four key steps:

• Donor screening
• Fecal collection
• Fecal preparation
• Administration

1. Donor Screening

The healthy donor horse is chosen according to the following criteria: ^[1][4][7]

• Deemed healthy upon physical examination
• No signs of dysbiosis or GI dysfunction
• Has not received antimicrobial therapy in the last three to six months
• No signs of colic
• No recent history of transportation, medical procedures, or probiotic interventions

In some cases, fecal matter is donated by more than one horse. ^[1]

2. Fecal collection

Manure is collected from the donor horse manually from the rectum or after excretion into clean straw bedding or a fecal collector. ^[1]

The freshness of the material is crucial for a successful FMT, as exposure to air can cause some bacteria in the manure to start degenerating. ^[1][4][9] After 6 hours, the microbial population begins to change in composition, potentially affecting the treatment’s effectiveness. ^[1]

It is also possible to freeze the fecal matter, although there may be some changes to the microbial composition upon freezing. More research in this area is required. ^[1]

A large amount of fecal matter is required for sample preparation, so collecting more than one bowel movement by the donor horse(s) is usually necessary. ^[1]

Most practitioners use fresh fecal matter, although some use centrifugation to separate the individual components of the donation. ^[1] Once the fecal matter is collected, it is screened for parasites and infectious agents. ^[1]

3. Fecal Preparation

A fecal solution is prepared by mixing the fecal matter (either fresh or frozen) with water, sodium bicarbonate solution, bismuth, or non-sterile saline. ^[1][7] Typically, the solution is still warm or is heated to body temperature before administration. ^[1]

4. Administration

The fecal solution is delivered directly into the stomach of the recipient horse through a nasogastric tube. ^[1]

Typically, the recipient horse gets 0.5 kg to 2 kg (1 – 4 lb) or 3 L (0.9 gal) of fecal preparation per transplant, repeated daily for 3 to 5 consecutive days. ^[1][7]

Side Effects

While the available research literature does not currently report any side effects of FMT in horses, safety remains a concern. It is still uncertain whether infectious diseases or harmful microorganisms could be transmitted to the recipient horse during the procedure. ^[1]

Ongoing research on equine FMT is focused on understanding both its efficacy and safety, aiming to identify potential risks and develop protocols to ensure it is a safe treatment option.

Directions for Future Research

More research is needed to determine whether FMT is an effective procedure for treating horses with diarrhea and colitis. ^[1] Further study is also required to confirm a standardized protocol for this method. ^[1]

Additionally, the safety of FMT needs to be clarified. This is especially true in terms of the transmission of infectious diseases and the introduction of harmful or unknown microorganisms into the recipient. ^[1]

Donor selection needs to be researched further as well. Determining what makes a horse’s gastrointestinal system “healthy” is a priority. ^[1][5]

Studies that investigate other factors involved in dysbiosis including nutrition, supplements and other potential treatments and how they might interact with FMT would also help create a holistic understanding of how FMT works. ^[10] This information would also help tailor protocols for the best outcome in each individual case.

Future research on how FMT might be used for overweight horses is also anticipated. Obese horses have alterations in their microbiota following weight loss. Transplantation may help rebalance their gastrointestinal systems. ^[1]

The possibility of establishing a Stool Bank for equine fecal samples would be useful to both the researchers and the practitioners in this field. It might be possible to gain deeper understanding not only into gut health as it relates to veterinary matters, but also to other characteristics of the horse such as sport performance. ^[1]

It is even possible that bacteria from high-performance horses could be transplanted to influence athletic performance in other horses. ^[1]

In human trials of similar procedures, a protocol where the recipient is administered a course of antibiotics before the fecal transplant has shown promise. Similar protocols have yet to be tested on horses and may prove even more effective than the current procedure. ^[1]

Frequently Asked Questions

Here are some frequently asked questions about fecal microbiota transplantation (FMT) in horses:

Summary

Fecal microbiota transplantation (FMT) involves transplanting fecal matter from the digestive system of a healthy horse to one with GI issues to help reinstate a healthy microbial balance. It is used to treat diarrhea and colitis related to dysbiosis.

• This procedure has been practiced in horse care for a long time but has recently gained a lot of attention especially with advances in FMT in human medicine.
• It is thought to be a safe, economical and effective treatment although some argue that the data available is still limited and no conclusions should be drawn at this time.
• During the procedure fecal matter is taken from a donor horse and administered to the recipient horse through nasogastric intubation.
• There are no reported side effects, but the safety of the procedure has yet to be confirmed.
• Future research is required to determine efficacy, prove safety, establish protocols, and understand possible new avenues for FMT.