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Digestibility of Horse Feeds: What Does It Mean?By Kentucky Equine Research Staff · September 12, 2016

Although the concept of digestion might be obvious to most horse owners, the idea of digestibility may be more elusive. Further, why horse owners need to know about the digestibility could also be somewhat unclear.

According to Kentucky Equine Research (KER) nutritionist, Kathleen Crandell, Ph.D., “Digestibility is a term used to describe the amount of nutrients that are actually absorbed by a horse and are therefore available for growth, reproduction, and performance in addition to body maintenance.”

There are two main ways to describe digestibility:

Apparent digestibility is an estimate of digestibility measured by subtracting the nutrients contained in feces from the nutrients in the diet. The resulting value is only an estimate because it does not account for nutrients lost as methane gas or as metabolic waste products excreted in the feces.

True digestibility is a more complex approximation of digestibility that corrects for the above-described nutrient losses.

“For example, understanding digestibility of energy sources—such as fiber, fat, starch, and sugar—is important when devising optimal diets for horses. A diet with lower digestibility provides less energy and might be more appropriate for easy keepers or those with insulin resistance,” advised Crandell.

She added, “In contrast, a ration with higher digestibility provides more energy and would be more appropriate for athletic horses or broodmares that are pregnant and lactating.”

For other types of nutrients, like vitamins and minerals, higher digestibility would mean a better source of that nutrient because of more efficient absorption.

To optimize your horse’s diet and to better understand feed labels and the results of feed analyses, consult an equine nutritionist.