Non-Fibre Carbohydrates in Dairy Diets

Most feed analysis labs now routinely report nonfibre carbohydrate (NFC) levels, also commonly known as nonstructural carbohydrates (NSC). The following are answers to the common questions about this relatively new "nutrient".

What Are Non-Fibre Carbohydrates?

Carbohydrates are made up of 2 fractions - the cell wall fraction and the non-cell wall fraction. The cell wall, or fibre, fraction consists of cellulose, hemicellulose and lignin and is the neutral detergent fibre value on an analysis sheet. The non-cell wall fraction consists of the highly digestible cell contents (starch, sugars and pectins) and is called the nonfibre carbohydrate.

Why is NFC Important?

NFC is a highly digestible energy source and, together with degraded protein, is needed by the rumen for microbial growth and digestion.

What is the Dairy Cow Requirement for NFC?

In general, NFC levels should be between 35-42% of the ration dry matter.

What Happens if the Dietary NFC Level Falls Outside This Range?

If the NFC level is low, there will be poor rumen microbial growth and digestion. Milk yield, body condition and protein test may be negatively affected. Incidence of ketosis may be increased in early lactation cows. If the NFC level is high, there is "too much" readily available energy and acidosis and low fat tests can occur.

How is NFC Analyzed?

NFC is not analyzed directly. It is calculated by subtracting the other feed components (NDF, CP, ether extract, ash) from 100.

Do Feeds Vary in Their NFC Levels?

Yes. Average NFC values for common feedstuffs are as follows: