Comparing Calories

At Tribute® Equine Nutrition, we do not broadly advertise the calorie contents of our products, as calories do not represent what is available for digestion, absorption and utilization by the horse.

Further, calories do not account for the energy expended by the animal to complete the digestion process. As an extreme example of the concept that all calories are not created equal, we can compare corn grain and oat straw (Figure 1). Corn and oat straw are IDENTICAL in Gross Energy, but due to differences in chemical composition and site of digestion, corn offers 980 kcal/lb greater Digestible Energy!

Figure 1. Comparison of Gross and Digestible Energy of corn grain and oat straw

Feedstuff Gross Energy, kcal/lb Digestible Energy, kcal/lb
Corn grain 2,011 1,760
Oat straw 2,011 780


The caloric value reported for horse feeds is generally Digestible Energy, which is an improvement over Gross Energy as it accounts for energy lost in the feces; however, this is just the first of several routes of energy lost from a feed that will impact it’s availability to support energy requirements for maintenance, growth, exercise, pregnancy and lactation (Figure 2).
Figure 2. Flow of feed energy through an animal
Flow of Feed Energy for Horses

The impact of these losses of energy have been quantified in other species but not in horses, such that we are limited in understanding the quality of a feed based on Digestible Energy calories alone. There are a number of ingredients that can be added to a feed to increase calories that add very little to the overall nutrition of the diet.
The Tribute® Equine Nutrition approach is to use high quality ingredients and include digestive support for the horse’s entire diet. Tribute brand feeds include Equi-Ferm XL, a pro- and prebiotic, as well as digestive enzymes to support optimal digestion. Enzymes enhance the digestibility of the concentrate portion of the diet and Equi-Ferm XL supports fermentation in the hindgut to maximize digestibility of the forage portion of the diet, which is the main source of dietary energy for the majority of horses. Additional fortification with highly available sources of nutrients commonly lacking in equine diets (amino acids, trace minerals, vitamins) support horse health and performance.
Calories alone will not support optimal horse health and performance, which is why we focus on being a reliable and affordable source of key nutrients.

Article By: Nicole Rambo, Ph.D.
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