Equine Intestinal Microbiome: Contrasts in Easy and Hard Keepers

Owners and veterinarians classify horses based on body type and metabolism as easy keepers, hard keepers, or somewhere in between. Easy keepers can maintain weight without difficulty, whereas hard keepers struggle to sustain appropriate condition. Could the key that unlocks the mystery of metabolism lie in the horse’s hindgut?

According to veterinary researchers, the intestinal microbiome—the population of beneficial microorganisms in the hindgut—may play a sizeable role in how different horses digest nutrients.

In their study^*, Johnson and Biddle collected fecal samples from 97 horses and studied the microbiomes using DNA analysis.

“The researchers found significant differences in the microbiome populations of easy and hard keepers, and these variations could alter or modify nutrient availability in horses,” explained Kathleen Crandell, Ph.D., a Kentucky Equine Research nutritionist.

For example, hard keepers had a reduced abundance of Bacilli (producers of lactic acid), Gammaproteobacteria and Verrucomicrobiae (both utilizers of amino acids). Horses with smaller populations of those bacteria may therefore be less efficient at accessing nutrients in the hindgut, which explains why they are harder to keep in optimal condition.

Additional analyses revealed differences in microbial populations involved in starch and sucrose metabolism, as well as nutrient transporter proteins between easy and hard keepers. Overall, horses with moderate metabolisms (“medium keepers”) appeared to be most efficient at nutrient digestion and host absorption.

The researchers concluded that “reduced bacterial abundance and functionality in hard keepers leads to insufficient nutrient levels to support a healthy microbiome and maintain horse condition.”

Crandell added, “Maintaining healthy microbial populations in the digestive tract can benefit horses in many ways and can easily be achieved by offering various dietary supplements.”

Examples of such products include:

• RiteTrac, which contains antacids that rapidly neutralize acid secreted in the stomach, providing a more neutral pH in the stomach, as well as a hindgut buffer to prevent hindgut acidosis;
• EquiShure, a time-released buffer targeting the hindgut, particularly useful in cases of high grain and high fructan intake; and
• Triacton, designed to maximize skeletal strength, buffer stomach acid to bolster gastric health and reduce the incidence of ulcers, and moderate the pH of the hindgut to prevent acidosis.

^*Johnson, A.C.B., and A.S. Biddle. Microbiome effects on metabolic efficiencies in easy and hard keepers. Journal of Equine Veterinary Science. 76:40.