ARS | Publication request: Profiles of Nonstructural Carbohydrates, as a Function of Species and Extraction Method, in Four Cool-Season Forage Grasses

Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: October 19, 2007
Publication Date: January 26, 2008
Citation: Kagan, I., Kirch, B.H., Strickland, J.R. 2008. Profiles of Nonstructural Carbohydrates, as a Function of Species and Extraction Method, in Four Cool-Season Forage Grasses. Society for Range Management Meeting Abstracts. Published on Compact Disc and distributed at meeting. Abstract #2314. http://srm.confex.com/srm/2008/techprogram/P2314.HTM

Technical Abstract: Nonstructural carbohydrates (NSC) of forage grasses, particularly long-chain fructans, have been proposed as the causal agent of equine laminitis. In order to evaluate the correlation between NSC and laminitis, NSC must be quantified in the forages being fed to and grazed by horses. The goal of this study is to optimize and validate an NSC extraction procedure by comparing and adapting some of the methods in four decades’ worth of fructan literature. NSC were extracted from four forage grasses collected randomly from established monoculture pastures in October 2006. Kentucky bluegrass (Poa pratensis), orchardgrass (Dactylis glomerata), timothy (Phleum pratense), and tall fescue (Festuca arundinacea), all common in central Kentucky, were extracted using methods that differed in temperature (boiling vs. ambient), duration (two versus three extractions), and sample preparation (ground with liquid nitrogen vs. macerated at 2-3mm in length). Short-chain and long-chain sugars were separated by high-performance liquid chromatography (HPLC) with pulsed amperometric detection (PAD). Regardless of the extraction method, concentrations of long-chain sugars (fructans) were much lower in tall fescue and bluegrass than in orchardgrass and timothy. Also, monosaccharides, particularly glucose, were the most abundant sugars in all extracts. Yields of long-chain NSC were optimized by increasing the number of times that the forage tissue was extracted. Three extractions produced more prominent peaks than two extractions, indicating greater NSC recovery. Extraction by boiling tended to yield more peaks, and greater peak surface area, than extraction at ambient temperature. These data comparing multiple NSC extraction methods are a first step in developing a robust chromatographic method for isolating fructans, which, in turn, will be used in feeding studies to rigorously evaluate the role of fructans in laminitis.