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The language of nutrition: NSC (Non-structural carbohydrates) and NFC (Non-fibrous carbohydrates)

Anna Foley Published on 06 November 2015

In layman’s terms, what does NSC and NFC mean?

NSC stands for non-structural carbohydrates, while NFC refers to non-fibrous carbohydrates.

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The concentrations of NSC and NFC in feeds are not the same (see Table 1); therefore, these terms should not be used interchangeably. NSC refers to the sugars, starches and organic acids, while NFC measures sugars, starches, organic acids and pectin.  1815pd language tbl 1

How is it measured?

NSC is measured in the laboratory by an enzymatic method. NFC is not measured in a laboratory; its value is calculated by difference:

NFC = 100 - (percent NDF + percent CP + percent EE (ether extraction) + percent ash) 

or 

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100 - [(percent NDF - NDIP) + percent CP + percent EE + percent ash)].

NDIP is neutral detergent insoluble crude protein. Researchers from Penn State University note that although the first equation is most commonly used, the second equation is preferred because it corrects for crude protein in the NDF. From the corn silage report:

NFC is calculated as: 100 - [(34.42 + (7.43 - 0.61) + 3.05 + 5.22)] = 50.49

What impact does it have on a ration?

Optimizing NSC or NFC in a dairy ration is an important key to maximizing milk and milk protein production.  

1815pd language fig 1

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Explain what this does in a ration.

The rumen microbes that pass to the small intestine supply 60 to 70 percent of the total protein/amino acid supply to the dairy cow. Propionate, which is an organic acid produced in the rumen, is the major precursor in ruminants for the production of glucose. Both glucose and protein are essential to maximizing milk and milk protein production.

The most important driver of microbial protein and propionate production in the rumen is optimization of NSC/NFC (starch, sugars and pectin) concentrations in rations. Grains and good-quality forages are the main sources of ration NSC/NFC.

When balancing rations for NSC, an acceptable range for lactating cows would be 30 to 40 percent on a dry matter basis. If NFC is used, then a range of 33 to 42 percent on a dry matter basis is acceptable.  PD

References omitted due to space but are available upon request. Click here to email an editor.

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