Equine fecal microbiota transplantation involves a veterinarian transferring feces from healthy horse into the gastrointestinal tract of a sick horse aiming to improve the microbiome and gastric health of the ill horse. However, researchers do not fully understand the method and a lack of standardization exists, especially in storage techniques used to preserve the product over time.

Finding the Best Way to Store FMT Product

Researchers recently evaluated the viability and diversity of both fresh and frozen fecal microbiota transplant (FMT) products to determine if they could be preserved for later use in horses with intestinal microbiome issues. For this, the team collected fresh feces from three healthy adult horses. They stored the feces in varying preservation solutions (saline with glycerol and saline only) and temperatures (-20 C or -80 C ) before assessing the bacterial populations in each sample.

They found that freezing the product at -80 C in a saline and glycerol preservative was most effective for maintaining healthy, viable microbial communities that could help address intestinal issues in horses needing transplant.

Future Applications for FMT

“I see the most useful application (of this storage method) being if a horse were to undergo an elective procedure where they were going to be receiving prophylactic antibiotics as part of the procedure,” said Alicia Long, DVM, Dipl. ACVIM, ACVECCS, assistant professor at the University of Pennsylvania’s New Bolton Center, in Kennett Square. “That way their feces could be saved prior to any changes that occur, (when the gut is) at its most normal.

“We know that antibiotics particularly have a huge effect on the gut microbiome, and it takes weeks to months to restore the normal microbiome after antibiotic administration,” Long added. If stored feces from the horse undergoing surgery are not available, then feces from a healthy horse from the same farm, and relatively the same age, could also be used for FMT, she added.

The next research step involves giving the frozen product to live horses and seeing if their microbiomes become more like that of the donor horse, said Long. Scientists could also evaluate the effect of an FMT transplant on horses with clinical conditions, such as colitis (inflammation of the large intestine, or large colon), to determine its effectiveness in resolving these issues.

Long said she hopes future studies will demonstrate that larger volumes of FMT product can be stored successfully, because horses with intestinal problems would need greater amounts for successful treatment.

The study, “Assessment of fecal bacterial viability and diversity in fresh and frozen fecal microbiota transplant (FMT) product in horses” appeared in BMC Veterinary Research, in July 2024.