Over the past few years, the feeding of carbohydrates has become a hot topic and major concern for many horse owners. Many are now voicing their apprehension with either feeding too much or finding the right balance of carbohydrates in their horse feed.

These concerns are warranted, as a diet too high in certain types of carbohydrates, primarily nonstructural carbohydrates (NSC), can lead to behavioral issues, obesity and/or other detrimental health issues. 

Carbohydrates are an important nutrient for your horse. They are actually the primary source of energy in a horse’s diet. The majority of carbohydrates in most equine diets is in the form of fiber (structural carbohydrates), which they get from their forage. However, in energy dense feeds, like a concentrate (horse feed), they are higher in what is called nonstructural carbohydrates (NSC).

  • Structural carbohydrates are found in the cell wall of the plant and, while generally called “fiber,” they are also known as cellulose or hemicellulose. Structural carbohydrates are digested by the horse with the aid of bacteria, primarily in the hindgut—the horse’s digestive enzymes do not have the ability to break fiber down.
  • Nonstructural carbohydrates are the sugars, starches, and fructans found within a plant’s cell. They play no role in the “structure” of a cell. Sugar and starch are readily digested by the horse, primarily in the small intestine by digestive enzymes, and are easily absorbed. Fructans are similar to structural carbohydrates and must be digested by bacteria to be absorbed, usually taking place in the hindgut.

Sugars and starches are found in horse forage, feeds and even certain supplements. Digestive enzymes in the small intestine break down sugars and starches into simpler sugars (monosaccharides), which are then absorbed into the bloodstream of the horse in the form of glucose. This is why it is important to look at both sugar and starch, because both are broken down to glucose.

Glucose is the source of energy for all the cells in a horse’s body. With a spike of glucose in the horse’s circulation, the hormone insulin is released by the pancreas. Insulin then directs glucose either to be stored in muscles or the horse’s liver as glycogen, which can be broken back down later into glucose. If these tissues have enough glucose, the excess glucose is then converted to fat.

The sources of NSC in a horse’s diet will vary. For many horses, sources of NSC in the diet come primarily from their hay. This is because while forages tend to be lower in NSC, they are consumed in large quantities each day. It is worth noting, young and lush forage can be high in sugars and fructans. You can learn more on this topic in our Transitioning Your Horse to Spring Pasture article. Depending on the conditions during growth and harvest, hay can be higher NSC than appropriate for a horse with metabolic issues. The only way to know the NSC of hay is to have it tested.

In the past, commercial feeds were higher in NSC since they relied on NSC-dense grains like corn, wheat, barley or oats with added molasses. More recent innovations utilize lower NSC ingredients to create horse feeds that add energy to the diet from highly digestible fiber and fat sources, rather than relying on sugar and starch.

Some approximate NSC values for some feeds include:

Where the topic of NSC becomes confusing for many is when owners ask how much NSC their horse needs in their diet? The question should really be how much energy is needed in the horse’s diet and in what form. For the non-metabolically challenged horse - these are those horses not suffering from insulin resistance, equine metabolic disease, or obesity - NSCs are an important source of energy. For example, a racing thoroughbred’s energy requirements will be much higher than that of a horse that is casually ridden. Thus, in a non-metabolically challenged horse that is racing, they will need more NSC (or energy) in their diet.

For metabolically challenged horses, sources of energy become very important. Generally, these types of horses’ energy requirements can be met by feeding a horse feed with a lower percent of NSC that is higher in fat. This can get particularly challenging with horses that require high energy diets, but it can be managed. You can learn more about this topic by reading our Low NSC for the Performance Horse article.

Overall, nonstructural carbohydrates are an important part of any horse’s diet. Yet, it can be quite challenging to find the appropriate balance of NSC in the diet for any horse. Therefore, please feel free to contact us for any advice and support that you may need in designing an adequate feeding plan for your horses.

Nicole Rambo, Ph.D., Chris Mortensen, Ph.D.