Foal Diarrhea and Prebiotics

At birth, a foal has a much different microbial population in its hindgut than its dam does. However, by two weeks of age the population of microbes is much the same for mare and foal.

One of the most important tasks of these microbes is fiber digestion, which is why very young foals don’t digest fiber as well as foals that are a few months old. Little is known about exactly how the microbes find their way into the foal’s digestive tract and become established in the proper ratio to pathogenic organisms that are also present. It is thought that diarrhea, common in young foals, might be a result of an imbalance of helpful and harmful microbes.

Noninvasive study of hindgut microbes has been made more efficient by the recent development of new methods of manure analysis. Using denaturing gradient gel electrophoresis (DGGE) and polymerase chain reaction (PCR) to look at feces from a mare and her foal, researchers can produce each horse’s microbial profile and compare these profiles between the two equines. This process typically shows the change as the foal’s hindgut environment becomes more similar to that of the mare.

A two-year study at the University of Kentucky was conducted to see whether treating young foals with a prebiotic, thus supporting the growth of populations of specific desirable microbes, would decrease the incidence and duration of diarrhea. In the first year, the group of treated foals showed fewer days when diarrhea was present than for untreated foals. However, in the second year, both treated and untreated foals in the study group had similarly low rates of diarrhea, so it was not possible to say that administration of a prebiotic had a significant effect on limiting diarrhea in this sample of young foals.

In the future, research will continue to examine the effect of treatment with both prebiotics and probiotics on the colonization and development of microbes in the gastrointestinal tracts of foals as well as the way these microbial populations develop and progress.