Study: Horses' Diets Affect Gastrointestinal Bacteria

Horses fed a diet of only forage have greater bacterial stability and fewer "bad" fecal bacteria, such as Streptococcus spp, than horses that are also fed concentrates. This finding, reported by a group of Swedish researchers, provides opportunities for the industry to develop more targeted feeding strategies to support equine health and welfare.

"Diets rich in readily fermentable carbohydrates, fed traditionally to meet the increased energy requirements of the performance horse, are associated with a number of gastrointestinal disorders that involve disturbances in the intestinal microbiota," wrote the research team, led by Professor Jan Erik Lindberg from the Department of Animal Science at the Swedish University of Agricultural Science.

In this preliminary study, researchers examined the impact of feeding a high-energy forage-only diet or a more traditional forage-concentrate diet on fecal microorganisms.

Lindberg and colleagues fed six mature Standardbred geldings in training either the forage-only or the forage-concentrate diets for 29 days. They extracted and analyzed bacterial DNA four times during the study period, measuring fecal pH and culturing bacteria on the last day.

According to the researchers, a forage-only diet "resulted in a microbial composition that was more stable and had lower counts of cultivable [lactic acid bacteria]." In addition, all study horses fed the forage-concentrate diet had motile and swarming Lactobacillus ruminis and significantly more Clostridiaceae cluster III in their feces than horses fed the forage-only diet.

The impact of these findings is unknown, relayed the authors.

This study is the first to describe changes in the uncultured bacterial populations of horses. Ultimately, the Swedish researchers hope to improve the intestinal health of horses and increase the body of knowledge regarding the relationship between diet and microbiota. Research concerning bacteria that appear and disappear with changes in diet is ongoing.

The study, "Changes in faecal bacteria associated with concentrate and forage-only diets fed to horses in training," will be published in an upcoming edition of the Equine Veterinary Journal. The abstract is available online.

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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