Carbohydrates and Horses
The majority of equine feeds consist of carbohydrates. For this reason, the type of carbohydrates fed to horses matters greatly.
Approximately three-quarters of dietary dry matter consists of carbohydrates. Horses use them as an energy source, making their selection and dosage particularly important when energy demand is high. Carbohydrates not needed for energy production are converted into fat.
Different Types of Carbohydrates
Carbohydrates include sugars, starch, and cellulose. They are typically divided into simple and complex carbohydrates. Different carbohydrates are absorbed at different rates. For example, starch provides energy more slowly than simple sugars or glucose, which enters the bloodstream very rapidly. While glucose does not occur directly in feeds, it is the structural unit and absorption form of nearly all carbohydrates. For this reason, “blood sugar” refers to blood glucose concentration.
Complex carbohydrates are divided into disaccharides and polysaccharides. Disaccharides are commonly referred to as sugars. The most well-known disaccharide is table sugar, which rapidly raises blood glucose levels. The most common polysaccharide is starch, found in grains at approximately 50–60%. Energy from starch is released more slowly, maintaining blood glucose levels for longer periods.
However, horses have a limited capacity to digest starch, with a commonly accepted maximum of about 1 kg per feeding for a 500 kg horse. Undigested starch passes into the large intestine, where bacterial fermentation lowers gut pH from neutral to acidic. Acidic conditions impair beneficial bacteria and promote harmful bacteria. For this reason, large concentrate meals should be avoided and divided into multiple feedings. For example, oats should generally be limited to about 2 kg per feeding, as they contain approximately 50% starch by weight.
One important polysaccharide is glycogen, or “animal starch.” It does not occur in feeds but is synthesized in the horse’s body. Excess sugar intake is stored in muscles as glycogen. During periods of high energy demand, such as competition, glycogen is mobilized for energy. Muscle glycogen levels directly affect muscular endurance.
Carbohydrates in Feed Analysis
Feed analyses typically do not list “carbohydrates” as a single value but divide them into nitrogen-free extract (NFE) and crude fiber. NFE includes easily digestible carbohydrates such as sugars and starch. As fiber content increases, NFE decreases, reducing digestibility. Good-quality hay typically contains about 50% NFE per kg of dry matter, while oats exceed 65%.
Crude fiber includes more difficult-to-digest carbohydrates such as cellulose. Fiber content reflects stem content in hay and hull content in grains. As fiber increases, digestibility and energy availability decrease. Late-harvested hay generally has higher fiber content, often exceeding the recommended upper limit of approximately 30% per kg of dry matter. High fiber content lowers energy density and increases the need for greater hay intake. Overall energy content is influenced not only by carbohydrates but also by fat and protein levels.
Source: Anneli Lillkvist, Feeding for Results
