Hydrolyzable carbohydrates in pasture, hay, and horse feeds: direct assay and seasonal variation

• Published in: Journal of animal science Vol. 79; no. 2; pp. 500 - 506
• Main Authors: Hoffman, R. M, Wilson, J. A, Kronfeld, D. S, Cooper, W. L, Lawrence, L. A, Sklan, D, Harris, P. A
• Format: Journal Article
• Language: English
• Published: Savoy, IL Am Soc Animal Sci 01.02.2001; American Society of Animal Science; Oxford University Press
• Subjects: Animal Feed - analysis; Animal productions; Animals; Biological and medical sciences; Carbohydrate Metabolism; Carbohydrates; Carbohydrates - analysis; Dietary Carbohydrates - metabolism; Fabaceae - chemistry; Fermentation; Food; Fundamental and applied biological sciences. Psychology; Horses; Plants, Medicinal; Poaceae - chemistry; Poaceae - metabolism; Regression Analysis; Seasons; Spectroscopy, Near-Infrared - veterinary; Terrestrial animal productions; Vertebrates; Farming animal; Herbivorous; Animal feeding; Fodder; Digestion; Experimental study; Fermentation; Hydrolysis; Vertebrata; Mammalia; Seasonal variation; Horse; MONOGASTRIC ANIMALS; Chemical composition; Carbohydrate; Perissodactyla; Ungulata; Feed
• ISSN: 0021-8812; 1525-3163; 0021-8812
• DOI: 10.2527/2001.792500x

Carbohydrates may be hydrolyzed or fermented in the digestive tract, and this distinction is important for the evaluation of the diet of herbivores. Both hydrolyzable and fermentable carbohydrates are included in the nonstructural carbohydrate (NSC) fraction as estimated by difference using proximate analysis. Our objectives were to measure hydrolyzable carbohydrates in forages and concentrates, to compare these values with nonstructural carbohydrate, to test for prediction of hydrolyzable carbohydrate concentration in forages from its near-infrared spectrum, and to examine seasonal variation of carbohydrates in pasture. Samples of forages (107) and concentrates (25) were collected, dried, ground, and analyzed for NSC (calculated as 100 - water - CP - fat - ash - NDF), hydrolyzable carbohydrate (CHO-H, direct analysis), and rapidly fermentable carbohydrate (NSC minus CHO-H). Hydrolyzable carbohydrate accounted for 97% or more of the NSC in the concentrates but only 33% in pasture and hay. A two-term polynomial equation fit all the data: CHO-H = 0.154 x NSC + 0.00136 x NSC2, R2 = 0.98, P < 0.0001, n = 132. In 83 pasture samples, CHO-H concentrations were predicted by near-infrared spectra with a calibration R2 of 0.97, a mean of 48 g/kg, and a SE of calibration of 3.5 g/kg DM. In pasture samples collected between September 1995 and November 1996, the coefficient of variation was 31% for both CHO-H and rapidly fermentable carbohydrate (CHO-FR); the largest increments were 31 g/kg of CHO-H from September to October and 41 g/kg of CHO-FR from February to March. The increased risk of certain diseases, such as laminitis and colic, that have been previously associated with an abrupt overload of NSC may be more precisely attributed to CHO-H in grain concentrates, and to CHO-H as well as CHO-FR in pastures.