Mare and Foal Nutrition Study Creates New Areas of Interest
Morgan Pyles, a PhD student in the department of animal and food sciences at the University of Kentucky (UK), became interested in mare and foal nutrition by accident.

“When I began looking into graduate school, I was deciding between equine reproduction research and equine nutrition research,” she said. “I worked with the reproductive health group in the UK Gluck Equine Research Center for the summer after finishing my undergraduate degree and met Dr. Laurie Lawrence (PhD, professor in the department of animal and food sciences at UK) through that study. She had a graduate student position available to start that fall, which helped make my decision to study equine nutrition.”

Pyles said Lawrence already had funding available for a study in collaboration with Michael Flythe, PhD, a microbiologist with the USDA Agricultural Research Service Forage-Animal Production Research Unit. The study focused on the effects of starch source on mare and foal hindgut bacteria, which became Pyles’ thesis study.

The study, entitled “Effect of Maternal Diet on Select Fecal Bacteria in Mares and Their Foals,” involved assigning pregnant Thoroughbred mares to one of two treatment groups: one group was fed an oat-based concentrate and the other group a corn- and wheat-middling-based concentrate. The team chose oats and corn as the starch sources in the pelleted concentrates because oats are considered more easily digestible for a horse, while corn and wheat middlings are slightly less so. These differences in digestibility would help demonstrate if these different starch sources in pelleted concentrates have different effects on the bacteria in the digestive tract. There were also prior studies conducted in Lawrence’s laboratory that indicated that starch sources have differential effects on the bacterial community in a horse’s hindgut.

Pyles, Lawrence, and their colleagues then collected fecal samples and evaluated the mares’ hindgut microbial community in late pregnancy, immediately after foaling, and post-foaling. The team examined the foals’ microbes after birth, as well.

Although no major issues occurred during the study, a few things made collecting the necessary data a bit trickier, Pyles said.

The first challenge, Pyles said, was predicting when the mares would foal, as one of the samples they wanted to collect was a pre-foaling sample close to parturition.

“Each mare is different and works on her own schedule,” she said. “Some mares are very predictable, as in we know she will foal before her due date every time, and others have few signs before they foal.”

Another surprising nuisance, said Pyles, was waiting for fecal samples from the foals.

“We found out through this study that foals do not defecate very frequently in the first few days after birth. So we spent a lot of time sitting and waiting for samples from foals,” she said

The study brought several things to light in regards to foal hindgut microbial colonization and nutrition.

“We collected samples within the first 24 hours after birth and we were surprised at the amount of bacteria already present,” Pyles said.

Cellulolytic bacteria, which are essential in adult horses’ hindguts, were actually slower to colonize in Pyles’ study.

Another surprise, Pyles said, was there was no differences between treatment groups in the mares, although there were some differences over time.

“There was a decrease in cellulolytic bacteria and lactobacilli just after parturition,” she said. “There are a lot of changes in the mare around parturition, therefore, it is not surprising that we saw some changes in bacteria around that time.”

There were treatment differences in the foals, however, which has helped open up new areas of study for the field of equine nutrition.

“We did see some differences between treatments in the foal bacteria, specifically in the first few days after birth, which is interesting because foals don’t typically consume much solid feed at that time,” Pyles said. “From these results, we are turning our attention to milk composition.”

The foal’s primary nutrition source is milk during his first few days of life. Due to the early changes in foal hindgut bacteria Pyles observed and the foal’s diet at this time, she believes that milk composition could play a vital role in microbial colonization, an important finding that the study helped demonstrate.

The study might also help with understanding the normal progression of microbes in the horse, from birth to adult, which can assist in correcting problems, such as pathogen proliferation, when they arise, according to Pyles.

Foal diarrhea is also an issue that, while not usually life threatening, can be a major economic loss. Pyles said that colonization of the hindgut with normal bacteria could help with this problem.

Meanwhile, postpartum mares are at a higher risk for colic, and a better understanding of the changes in microbes around parturition could help with this problem as well, Pyles said. This study helps put research on the right track to investigate this area more.

“There is very little research investigating the changes in microbes in the mares GI (gastrointestinal) tract around foaling,” Pyles said. “Changes in bacteria have been associated with many negative health effects such as laminitis and colic. Therefore, understanding what the microbes are doing around this time (postpartum) and developing strategies to prevent upsets may provide some health benefits for the postpartum mare.”

Pyles said foal development is definitely a “hot topic” in the equine research industry, and her study has opened the doors to new possibilities for research in the diet of the mare and foal.

Maddie Regis is a sophomore marketing major at UK and communications and student relations intern within UK Ag Equine Programs.

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More information on Gluck Equine Research Center and UK Ag Equine Programs.