NSC (non-structural carbohydrates)

What it is

NSC are the carbohydrates that don't form part of the plant's structure. The University of Tennessee lab calculates NSC as WSC plus starch ^[1]. A related figure, NFC (non-fibre carbohydrates), also includes pectin and fermentation acids, so check which one a report gives ^{[1, 2]}.

Why it matters

Feeding a diet high in NSC over a long period has generally reduced insulin sensitivity compared with forage- or fat-rich diets, although the relationship is not straightforward ^[3]. For horses with insulin dysregulation, hay with low NSC (under 10%) is recommended to limit insulin responses ^[3]. Owners of horses with metabolic disorders commonly try to keep NSC below 10% ^[4].

Grains and cereal-based feeds, fruit, carrots, apples and treats should generally be left out of the diet of horses with equine metabolic syndrome because of their high NSC content ^[3].

Lowering NSC

Soaking hay for 7–16 hours at ambient temperature lowers water-soluble carbohydrates by 24–43%. In warm conditions, limit soaking to 1–2 hours because of microbial growth, and balance the minerals and vitamins that soaking leaches out ^[3].

Haylage produces a larger insulin response than hay with the same NSC content, so it is not recommended for horses with insulin dysregulation ^[3]. Cutting hay early and drying it quickly can help keep NSC down ^[4].

Reading it on a test

Hay tests report values both as fed and on a dry matter basis; compare feeds on the same basis ^{[4, 2]}.

See also starch, sugar wsc, sugar esc, dry matter.