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Veterinarians prescribe antibiotics every day to fight possible life-threatening infections. In some cases, these antibiotics cause diarrhea, which can be risky, especially if antibiotic-associated diarrhea (AAD) is accompanied by laminitis. While fecal transplantation has the potential to reduce AAD when used in conjunction with antibiotics, researchers must fine-tune the technique prior to widespread use.

The process of fecal transplantation involves taking feces from a healthy horse with a stable intestinal microbiome and delivering it to the intestinal tract of a diarrheic horse via nasogastric intubation.

“The goal is to deliver beneficial microbes—such as bacteria and fungi—from the healthy horse to the intestinal tract of the diarrheic horse to resolve disruption of the microbial flora, also called dysbiosis. This may work by repopulating the hindgut with healthy microbes or even suppressing the growth of pathogenic bacteria,” explained Catherine Whitehouse, M.S., a Kentucky Equine Research nutrition advisor.

According to her, “A healthy intestinal microbiome promotes whole-animal health. Any shift in the microbiome, such as what can occur following antibiotic administration, can have far-reaching effects on the overall health and well-being of the horse.”

Rather than waiting for AAD to hit, an alternative approach involves using fecal microbiota transplants prophylactically to avoid diarrhea in horses starting a course of antibiotics.

This approach was recently explored by veterinarians associated with the Japanese Racing Association’s Equine Research Institute.* In that study, nine healthy horses were divided into three groups and administered either the antibiotic metronidazole, both metronidazole and a fecal transplant, or neither (control group). Fecal samples were collected from all horses on day 0 of the study prior to treatment, on days 1, 3, and 5 of treatment, and again 15 and 30 days after the start of the study.

A single horse free of Clostridium difficile, Clostridium perfringens, and Salmonella spp. donated fecal samples. Each recipient horse received one liter of a fiber-free fecal suspension via nasogastric tube on days 1-5 of the study when treated with metronidazole.

While the fecal transplant theory holds promise, the results did not support using prophylactic fecal transplants in horses receiving oral metronidazole.

“Dysbiosis was appreciated in all horses treated with metronidazole regardless of whether they received a fecal transplant or not,” relayed Whitehouse.

Specifically, Clostridiaceae, Ruminococcacea, and Peptostreptococcaceae families decreased in abundance, whereas Enterobacteriaceae, Actinomycetaceae, and Aerococcaceae increased in all metronidazole-treated horses compared to the untreated controls.

“There may be several reasons why this study didn’t show a beneficial effect of prophylactic fecal transplants on AAD. These results do not necessarily mean this approach won’t be effective once the method is refined through additional research,” said Whitehouse.

For example, the metronidazole may need to be administered separately from the fecal transplant. In this study, the fecal transplant and metronidazole were administered concurrently, which means the metronidazole might have directly altered the composition of the transplant. In addition, the donor fecal samples used in this study were frozen upon collection and thawed prior to administration, which might have affected microbial viability. Also, whether or not the microbes remain viable after passing through the acidic stomach environment before reaching the large intestine remains unknown.

Whitehouse added, “Further research into the benefits and practical applications of fecal transplants are warranted. In the meantime, consider proven nutritional solutions such as digestive buffers that can help promote a healthy microbiome during times of stress. One such buffer is EquiShure, formulated by Kentucky Equine Research.”

*Kinoshita, Y., H. Niwa, E. Uchida-Fujii, T. Nukada, and T. Ueno. 2002. Simultaneous daily fecal microbiota transplantation fails to prevent metronidazole-induced dysbiosis of equine gut microbiota. Journal of Equine Veterinary Science:104004.

 

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