Physiological Functions of Equine Nutrition

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(Carbohydrates and Fats)

Anne Rodiek, Ph.D.

Californa State University, Fresno

Feeding horses is both a science and an art. Horses have done well on a wide variety of diets for hundreds of years. While evolved as a roaming and nibbling eater, horses have adapted to confinement and meal feeding. While evolved on a diet of fibrous feeds, horses have adapted to highly digestible, high energy rations. While man has tried a myriad of dietary manipulations to cause horses to perform better in the service of man, horses have remained robust and still willing to serve man. From a large view, it could be summated that horses have done an amazing job at continuing to do what they do in spite of what man has fed to them, rather than because of it.

DIGESTION, METABOLISM AND FEEDS

The digestive system of the horse is designed to maximize digestion of both high and low quality feeds. The small intestine is the site of enzymatic digestion of soluble carbohydrates, proteins and fats, the components of which are absorbed into the circulation. Insoluble carbohydrates pass to the cecum and colon where they are fermented by bacteria and protozoa, similar to those of the ruminant. Prececal digestion is relatively rapid, while postileal fermentation is quite slow with total rate of passage exceeding 24 hours. Although with large variability depending on diet and physical form of the feeds. This anatomical arrangement allows enzymatic digestion by the horse before fermentation by microbes ensuring that high quality nutrients are absorbed directly by the horse and are not converted to lesser quality nutrients by the microbes.

More than 70% of the horse’s daily feed intake is used to provide energy to fuel the horse’s metabolism. Traditional horse feeds are comprised primarily of carbohydrates with very little (less than 5%) fat. However, research over the past twenty years has shown that horses absorb and utilize fat efficiently. As such, both carbohydrates and fats (and to a lesser extent protein) can be used as energy sources for all activities of horses.

Carbohydrates

Plant materials contain both structural and nonstructural carbohydrates...

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