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NSC is nonstructural carbohydrates and there is much confusion and inconsistency in the horse industry on how to evaluate carbohydrate content in feeds. Percent NSC is often the request I receive but is not a value that I use in discussion unless the evaluation is clearly defined. In this fact sheet % NSC is defined as a combination of two analyses: starch and water soluble carbohydrates. % NSC was originally a calculated value that did not really reflect valuable information on carbohydrate content. Now the value is used loosely, a catch-all expression. It may represent just starch, or starch and WSC (water soluble carbohydrates), or WSC and ESC (ethanol soluble carbohydrates), or an empirical estimate, or only fructans. This confusion not only exists with horse owners but also in the veterinarian community. The % NFC, non-fiber carbohydrate, is now the mathematical calculation of starches, sugars, etc. and one that I do not use professionally in evaluating carbohydrate content of feeds.
A simple overview of what each provides:
- Laboratory analysis of starches; some are resistant to small intestine digestion (that is broken down by enzymes)
% ESC – ethanol soluble carbohydrates
- Laboratory analysis that represents carbohydrates digested in the small intestine; they are the carbohydrates that produce a true glycemic (blood sugar) response
% WSC – water soluble carbohydrates
- Laboratory analysis that includes simple sugars, oligosaccharides (several sugar molecules hooked together) and fructans
% NSC – nonstructural carbohydrates
- For this fact sheet %NSC represents a combination of two analyses, starch and water soluble carbohydrates, thus including simple sugars, oligosaccharides starches and fructans
% NFC – non-fiber carbohydrates
- Is a calculated value and is supposed to represent the simple sugars, oligosaccharides, starches, soluble carbohydrates, pectins, and fructans. Errors in the % NFC estimation are because it’s not a direct laboratory assessment, but a math calculation based on other analyses or estimates. % NFC is estimated by difference: 100% of dry matter minus the percentages of CP, NDF, ether extract, and ash.
The laboratory analyses that provide useful information are % starch, % ethanol soluble carbohydrates (ESC) and % water soluble carbohydrates (WSC). These three analyses provide different information. Thus, depending on the concern, (such as insulin resistant, laminitis, PSSM, colic, etc.) the analysis that is used is dictated by the issue/illness being addressed.
Below is a table of hay pellets sold by Star Milling that provides data on starch, sugar, and other nonstructural carbohydrate components as well as the minerals, Calcium (Ca) and Phosphorus (P).
Hay Pellet Starch, Calcium & Phosphorus Data*
|Hay Pellet||% WSC||% ESC||% Starch||% Starch + % ESC||% NFC||% Ca||% P|
|Hay & Grain 3/8 pellet||5.7||4.2||5.3||9.5||28.8||0.97||0.21|
|Alfalfa Bermuda 3/8 pellet||6.4||5.4||1.2||6.6||20.3||1.01||0.22|
|Oat hay ¼ pellet||6.3||5.3||0.7||6.0||12.0||0.26||0.12|
|Bermuda ¼ pellet||7.7||6.0||3.3||9.3||21.7||0.37||0.18|
|Alfalfa ¼ pellet||7.8||8.1||6.4||14.5||28.2||1.10||0.27|
|Timothy ¼ pellet||14.5||9.3||1.3||10.6||19.8||0.33||0.22|
|Alfalfa 3/8 pellet||6.0||5.2||5.1||10.3||23.8||1.11||0.23|
|Alfalfa Oat 3/8 pellet||6.2||7.2||2.7||9.9||23.2||1.10||0.21|
|Alfalfa Timothy (50/50) ¼ pellet||7.6||6.0||1.4||7.4||19.3||0.79||0.17|
*Values reported on as sampled or as fed basis.
- WSC is water soluble carbohydrates
- ESC is ethanol soluble carbohydrates
- NSC is nonstructural carbohydrates with NSC = Starch + WSC.
- Fructan content of feeds will vary but a crude estimate can be calculated by subtracting ethanol soluble carbohydrates from water soluble carbohydrates.
- % NFC is non-fiber carbohydrates