Innovation Development Manager, Consumer Nutrition Cargill Animal Nutrition
Over the past several years, a key focus in the equine industry has been in feeding low amounts of starch and sugar to reduce the risk of some metabolic disorders such as colic, laminitis and developmental orthopedic disease. We have even gotten questions about feeding low or no carbohydrates to horses. As this phenomenon has swept our industry, we need to take a step back to understand the different types and functions of carbohydrates and the importance that each brings to the horse.
Plant carbohydrates are broken down into two components: cell wall content and cell content. The cell walls contain cellulose, hemicellulose, glucans, pectins, gums and lignin and are typically known as the fiber portion of the plant. The cells contain starches, sugars, fructans, oligosaccharides, and fructooligosaccharides and are commonly thought of as the nonstructural carbohydrates (NSC). As plants are incorporated into feeds, the horse ingests all of these components.
The fiber portion provides the majority of energy for the horse and is not digested in the small intestine. Digestion occurs in the cecum and large intestine by the microbes and absorbed as volatile fatty acids. The efficiency of energy utilization from fiber is less than that from starches and sugars.
There are many ways to discuss carbohydrates and some of the common terms and definitions are listed.
Non-fiber Carbohydrates, or NFC – This measurement is a calculation, not an analysis, based on the common lab analysis.
100 (Protein-Fiber-Moisture-Ash-Fat) – This fraction contains starches, sugars and soluble fibers. It can be a good indicator of the amount of starch and sugar in grains, but needs to be used with caution in ingredients with high levels of soluble fiber, such as soybean hulls and beet pulp.
Nonstructural Carbohydrates, or NSC – This fraction is analyzed and is composed of starch and sugar. Starches and sugars are enzymatically broken down by the small intestine but the horse digestive system is not set up for large intakes of starch and sugar. Sugars are typically broken down very rapidly in the small intestine. Starches on the other hand can range from fast (oats) to slower (corn) digestion in the small intestine. Fast digestion means most occurs in the upper small intestine while slow digestion means most occurs at the end of the small intestine. If the small intestine is overloaded with starch, the chance for some to leak to the hindgut increases. Once starch leaks into the cecum of a horse, rapid fermentation will produce lactate, the pH decreases, some beneficial microbes are killed and gas production increases. This increase in gas production in the cecum of the horse causes severe discomfort and in some cases death. Overloading the digestive system with NSC can lead to metabolic disorders such as colic, insulin resistance, founder and developmental orthopedic disease. Also, NSC play a major role in managing the glycemic response of feeds – higher NSC typically indicates higher glycemic response. A good way to control the glycemic response and to reduce the chance for starch to leak to the hindgut is to combine different starch types so digestion will occur in different areas of the small intestine not just one. A few ingredients that have low NSC values are soybean hulls, wheat middlings, beat pulp and alfalfa. A few ingredients with high NSC values are corn, oats and barley.
Water Soluble Carbohydrates, or WSC – This fraction is subset of NSC and is calculated by removing the starch component. When soaking hay or forage this portion is removed reducing the amount of sugar intake from the forage.
Fructans – Sugars that are found in some cold season grasses such as fescue, orchard grass and timothy. The enzymes in the small intestine do not break down fructans. Microbes in the large intestine can break fructans down and the result is similar to NSC leaking to the hindgut. If too much reaches the hindgut, colic or laminitis can occur.
Neutral Detergent Fiber, or NDF – This is a measure of the insoluble fiber (see insoluble fiber for function) fraction of an ingredient. NDF contains hemicellulose, cellulose, lingo-cellulose and lignin.
Acid Detergent Fiber, or ADF – This fraction is a subcomponent of NDF that contains everything except hemicellulose. This term is not displayed on many feeds but can be an indicator of energy content of the feed, with the lower the ADF content the higher the energy content of an ingredient.
Soluble Fiber – Analysis that contains gums, mucilages, pectins and algal polysaccharides. This is not conducted on a routine bases in horse feeds due to the cost and complexity of the analysis. This type of fiber is fermented in the hindgut but does not have the negative effects like rapid increase in lactate and lower pH as seen when starches are rapidly fermented.
Insoluble Fiber – Analysis that contains hemicellulose, cellulose and lingo-cellulose. Insoluble fiber is very similar to NDF except for the lignin portion. This is not conducted on a routine bases in horse feeds due to the cost and complexity of the analysis. The lowest potential energy source of feeds is the insoluble fiber fraction. However, insoluble fiber is important in maintaining normal gastrointestinal motility and function.
Carbohydrate nutrition is vital for the safety and performance of horses. Remember that feeding low-carbohydrate diets to horses are unfeasible but varying the starch and sugar levels can be beneficial depending on the type of horse you have. If you have a performance horse, a higher intake of starches and sugar may be needed to get the energy and glycogen repletion to match the type of exercise. However, lower levels of starches and sugars are needed for horses that are obese, have digestive issues, tie up or founder.
Take home points
1. Understanding the carbohydrate fractions (fiber vs. starch vs. sugar) is very important to giving proper nutritional care to your horse.
2. Talk to an equine nutritionist about the type of diet that best fits your horse’s needs. Many qualified feed representatives can help you pick the right product for your horse.
3. Understanding the nutrients in your entire feeding program is important. Intake is the key, not percentages, so knowing the nutrients in your grain feed, forage and supplements, and feeding the appropriate amounts will improve the safety and performance of your horse.
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11/4/09 - 11:23PM