Over the past few years, the feeding of non-structural carbohydrates (NSC) 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. Diets high in NSC have been linked to metabolic and digestive disorders ranging from obesity, laminitis, and colic. It has also been linked to Equine Metabolic Disease (EMD) and can be a contributing factor to developmental orthopaedic disorders (DOD) in young, growing horses. Thus, it is important that owners are aware of what exactly NSC is and how it can affect their horses.
What is NSC?
Carbohydrates are an important nutrient for your horse. In fact, they are the primary source of energy in a horse’s diet. The most common form of carbohydrate in the horse’s diet is in the form of fiber, or what we call “structural carbohydrates.” Alternatively, in grains, the carbohydrates are in the form of what we call non-structural carbohydrates (NSC). Yet, it is important to remember that forages, while less energy dense, do also provide NSC to the horse.
- Found in the cell walls of the plants (forage) horses eat.
- Found in the outer covering of many grains, but in limited quantities.
- The common name is fiber, but they are also known as cellulose and hemicellulose.
- There are no enzymes in the digestive system of the horse that can digest structural carbohydrates. Thus, the structural carbohydrates that horses consume are only digested with the aid of the gut microbes, which are primarily located in the hindgut. Here, they help break the fiber down to provide the energy horses needs to survive and thrive.
- The sugars, starches, and fructans found within the cells of the plants (forage) horses eat.
- NSCs are also found in the fleshy or interiors of grains.
- Sugars and starches are readily digestible by the horse by enzymes, primarily in the small intestine.
- Fructans are like structural carbohydrates, as they require the hindgut microbes to be digested.
Sugars and starches are found in the horse’s forage, their concentrated feed/grain, and even in some supplements. Through digestion, sugars and starches are broken down by digestive enzymes in the small intestine into simpler sugars, which are called monosaccharides. These are then absorbed into the bloodstream of the horse in the form of glucose. Therefore, equine nutritionists look at both the amount of sugar and starch in the horse’s diet, as both are broken down into 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 directs glucose to either be stored in the muscles or in the horse’s liver as glycogen. This glycogen can later be broken down into glucose as needed by the horse. If the tissues have enough glucose/glycogen, then the excess is converted to fat.
NSC In Your Horse’s Diet
The sources of NSC in a horse’s diet will vary. For many horses, sources of NSC primarily come from their forage. Even though forage is lower in NSC on a per pound basis as compared to most horse feeds, most horses consume large amounts of forage per day. This is especially true of younger and lush forage; these can be much higher in sugars and fructans and is why caution is usually advised when allowing horses to graze on spring pastures with lush green forage.
Likewise, certain forages can either be high or low in NSC. This will be dependent on the species of the forage. For hay, factors such as the conditions it was grown under and conditions under which it was harvested can also impact NSC levels. The only certain way to know the NSC content of any forage is to have it tested.
When it comes to horse feeds, in days past, they were higher in NSC due to being dependent on NSC-dense grains, like corn, wheat, barley, or even oats. The addition of molasses also increased the NSC of the feed. This is still observed today in some lower quality and cheaper horse feeds.
Today, high quality horse feeds are comprised of lower NSC ingredients due to the negative impacts of high NSC diets on horse health and its contribution to EMS and other disorders. These more modern horse feeds contain added energy (calories) in the form of highly digestible fiber (structural carbohydrates) and fat sources, rather than sugar and starch (NSC).
Some approximate NSC values for some horse feeds and ingredients include:
- Beet pulp: 8-12% NSC
- Corn: 75% NSC
- Barley: 60% NSC
- Oats: 52% NSC
- Molasses: 54% NSC
- Kalm Ultra®: 23.5% NSC
- Kalm ‘N EZ®: 13.5% NSC
How Much NSC Does My Horse Need in Its Diet?
Where the topic of NSC becomes confusing for many is the question of how much NSC our horses need in their diet? The real question horse owners need to ask is, “how much energy is needed in my horse’s diet and in what form?”
For horses that are not faced with metabolic issues, like Equine Metabolic Syndrome or PSSM Type 1, NSC can still serve as important energy sources. This can be especially true of horses that compete or are under intense exercise, such as racehorses. With these types of horses, their energy requirements are much higher than horses that are casually ridden.
For horses that are metabolically challenged, the type of energy within their diet can become very important. Generally, these horses’ energy requirements can be met with a lower NSC percentage feed. The energy in their diet can be bolstered with the addition of fat. Where this becomes challenging is for metabolically challenged horses that are under intense exercise or require high energy diets. Yet, these can generally be managed with carefully balanced low NSC diets.
Every horse is different, and some may require special care. If you have questions about your horse’s nutrition plan, you can contact us for any advice or support.
Equine-Analytical Feed Composition Library. NSC values can be found at: https://equi-analytical.com/
Hoffman, R. (2009). Carbohydrate metabolism and metabolic disorders in horses. R. Bras. Zootec. 38:270-76.
National Research Council. (2007). Nutrient requirement of horses. 6th rev. ed. National Academies Press.