Carbohydrate Fractions of Forages Fiber Fractions. Week 3 Lecture 9 Clair Thunes, PhD Fiber Chemically fiber is a mix of cellulose, hemicellulose, pectins, lignin, indigestable protein and fats. Most measures of fiber developed for ruminants not hindgut fermenters This system doesn t fit the physiology or metabolism of the horse very well Different methods for different types of feed Term fiber gets used to describe NDF, ADF, CF, TDF etc. Total Digestible Fiber TDF includes cellulose, hemicellulose, Oligosaccharides, non-alpha glucose polymers, lignin, pectins, mucilages, gums, waxes, cutin some other stuff. TDF is relevant hindgut fermenters TDF is recognized as an official method with the AOAC 1
Neutral Detergent Fiber NDF part of the detergent method developed by Van Soest popular for measuring cell wall components Actually partitions forage DM into fractions based on bioavailability to ruminants. Original method provides the % cell wall in the feed or the cellulose, hemicellulose, and lignin. More recently amalyase has been added to the method to remove contamination from starch and is known as andf, is the recommended method for the National Forage Testing Association. Does not recover fructans, pectins, gums, mucilages, beta-glucans or soluble hemicellulose. Acid Detergent Fiber Is a way of preparing a sample for the sum of cellulose, lignin determination, insoluable ash and silica. Hemicelluloses can be estimated by subtracting the ADF from NDF. Accuracy depends on the sample and best if the ADF procedure is done on the same sample that had the NDF procedure. Crude Fiber CF contains errors in the determination of structural and nonstructural carbohydrates Most significantly the solubilization and loss of part of the lignin, cellulose and hemicellulose in the preparation. Still used though on feed tags. 2
Carbohydrate Fractions of Forages Non- Fiber Fractions. Nonfiber Carbohydrate No really satisfactory methods of assessing the NFC exist even though it is a major contributor to of the energy in a feed NFC s are those carbs not included in cell walls and not recovered by the NDF analysis. NFC=100-(protein + (NDF NDICP) + fat + ash) NDICP = non digestible insoluble crude protein, and includes sugars, starches, fructans, galactans, pectins, beta-glucans, and organic acids. NDICP not calculated as part of proximate analysis Nonfiber Carbohydrates For feeds %NFC is simplified to = 100 (%CP + %NDF + %EE + %ash) 3
Water Soluble Carbohydrates WSC s include compounds soluble in cold water Include monosaccharides, disaccharides, oligosaccharides, and some polysaccharides Also includes fructans WSC + starch = NSC depending on method used NSC = nonstructural carbohydrate is NOT the same as NFC NFC includes pectins and gums which are not included in NSC Ether Soluble Carbohydrates ESC is a component of WSC. ESC are ether soluble sugars eg glucose, fructose, sucrose but NOT fructans Subtracting ESC from WSC gives a crude estimate of fructan Starch Starch is just starch Measured by acid or enzyme hydrolysis There is an AOAC method for starch 4
Judging Forage Quality. Starch Analysis Visually Color should be bright Maturity (stem:leaf) presence of seeds etc Molds Weeds Pests blister beetle Smell Should smell sweet http://www.agry.purdue.edu/ext/forages/publications/id-190.htm 5
Selecting Hay. http://www.das.psu.edu/research-extension/equine/penn-state-horsenewsletter/articles/hn200910-04 http://www.das.psu.edu/research-extension/equine/penn-state-horsenewsletter/articles/hn200910-04 6
Benefits of Pasture Management. 7