Young foals with diarrhea don’t have the same bacterial richness in their feces as their healthy counterparts, research shows.
Diarrhea affects up to 60% of foals during the first six months of life. A single causative agent is often not identified.
Little is currently known about the fecal bacterial microbial richness and diversity of foals at a young age and what effect diarrhea has on its make-up.
Dr Angelika Schoster and her colleagues set out to compare the fecal bacterial microbiota of healthy foals to foals with diarrhea at up to two and four weeks of age.
Samples were collected from 20 foals born on Thoroughbred and Standardbred farms in Ontario, Canada. The first sample from each foal was taken during the first two weeks of life and the second between 15 and 28 days.
Nine of the foals developed diarrhea at some point during the study (experienced personnel on the farms were monitoring the daily consistency of the animal’s feces).
Precise timings of when samples were collected depended on farm management practices and whether a foal had diarrhea at the time of sampling, which was always within two days of its occurrence.
None of the foals used in the study had received antibiotics, probiotics or anti-inflammatary drugs.
The samples underwent DNA analysis.
Differences in microbial community composition based on age and health status were observed on all taxonomic levels, the researchers reported in the journal BMC Veterinary Research.
Of 117 enriched species in healthy foals found at the later time point, 50 of them (48%) were Lachnospiraceae or Ruminococcaceae, both of which are members of the Clostridia class.
“Lachnospiraceae and Ruminococcaceae … have been implicated as having important roles in gastrointestinal health in numerous animal species,” the researchers said.
“In humans and animals with gastrointestinal disease these species were consistently under represented, independent of the cause of gastrointestinal disease.
“Clostridia,” they noted, “are major producers of short chain fatty acids, which are important for intestinal and general health.”
Foals with diarrhea had a significantly lower richness in their gut microbiota, with Lachnospiraceae and Ruminococcaceae underrepresented when compared with the foals without diarrhea.
The findings, they said, suggest that potential preventative and therapeutic measures should focus on providing and maintaining a diverse and rich bacterial microbiota, in addition to defining and modifying the key bacterial species for gastrointestinal health, such as members of the Lachnospiraceae and Ruminococcaceae.
Discussing their findings, the authors said the bacterial microbiota of foals was assumed to play an important role in diarrhea, and early colonization and development was a dynamic process.
“In this study, significant impacts of both age and diarrhea were noted, with the most evident influential factor being age.”
Knowledge of the bacterial microbiota in foals was still in its infancy, they said.
“Initial culture-based studies tended to focus on a narrow spectrum of the fecal bacterial microbiota, such as lactobacilli, enterococci and clostridia.
“Subsequent culture-independent studies have provided much more insight into the rapid development of the bacterial microbiota.
“Foals develop a rich and diverse bacterial microbiota early in life, and it has been previously reported that the foal’s fecal bacterial microbiota resembles that of adult horses by 60 days of age.”
There were, they said, many significant differences in the fecal bacterial microbiota even over the relatively short time-frame of the study, highlighting the dynamic nature of the microbiota.
The most abundant bacterial phyla identified were Firmicutes, Verrucomicrobia and Proteobacteria, with the most abundant families being members of the Clostridia class, Ruminococcaceae and Lachnospiraceae.
While optimal levels of richness in bacterial microbiota were not known, diversity was thought to be of use as it may be more adept at fulfilling a wide range of necessary functions and be more resilient in the face of changes, such are dietary adjustments and stress.
“The complexity of the fecal bacterial microbiota, and the finding that bacterial alpha diversity is decreased in foals with diarrhea raises questions about common approaches to prevention or treatment of diarrhea.
“Metronidazole is commonly used to treat diarrhea in horses and sometimes foals. Many members of the Clostridia class are susceptible to this drug.
“Therefore, treatment could potentially inhibit the beneficial components of the fecal bacterial microbiota.
“Probiotics are also commonly used, although to date several studies have not shown any clear benefit for treatment or prevention of diarrhea in foals.
“One potential reason could be that the organisms found in most commercial probiotics (e.g. enterococci, lactobacilli) are not those found to be important members of the healthy bacterial microbiota in several studies, including our study.
“This raises questions about the potential efficacy of conventional probiotic organisms for the treatment or prevention of diarrhea, especially when they have to compete in such a rich and abundant existing bacterial microbiota.”
The authors noted that more females than males were affected by diarrhea.
“Females could have inherent differences in fecal bacterial microbiota composition compared to males, which could influence results of the effect of diarrhea. This has not been studied in horses, but has been investigated in human medicine, and differences in microbial composition between men and women are present.
“It cannot be predicted to what extent and in which way this would have influenced our results.”
The researchers were variously affiliated with the University of Guelph in Ontario, Canada; the University of Zurich in Switzerland; the University of Copenhagen in Denmark; and the Ross University School of Veterinary Medicine in St Kitts and Nevis.
Comparison of the fecal bacterial microbiota of healthy and diarrheic foals at two and four weeks of life
A. Schoster, H.R. Staempfli, L.G. Guardabassi, M. Jalali and J.S. Weese.
BMC Veterinary Research 2017 13:144 DOI: 10.1186/s12917-017-1064-x