cropsci_c08-01-0006 Coblentz.indd

Methods previously used to measure recoveries of dry matter (DM) from forages following natural or simulated rainfall often have relied on simple gravimetric techniques, which yielded inconclusive estimates of DM recovery. Our objective was to evaluate insoluble cell-wall constituents as internal markers for estimating recoveries of DM from alfalfa (Medicago sativa L.) or alfalfa– orchardgrass (Dactylis glomerata L.) mixtures subjected to simulated rainfall. Forage mixtures consisted of 1000, 750, or 500 g kg−1 alfalfa, with the balance comprised of orchardgrass. Regardless of the forage mixture, concentrations of all cell-wall constituents increased (P ≤ 0.053) in response to wetting (0, 70, 140, 280, 420, 560, or 840 mm at 70 mm h−1) under a rainfall simulator. Following treatment, recovery of all cell-wall constituents was high ( ≥901 g kg−1). Generally, losses were smallest for neutral-detergent fi ber (NDF) markers regardless of analysis method (with alpha-amylase, sodium sulfi te, neither, or both), acid-detergent fi ber (ADF), and cellulose and largest for hemicellulose and lignin. Linear regressions of recoveries of DM by internal markers on values determined gravimetrically were good (r2 ≥ 0.775) when NDF was used to estimate recovery. In all these cases, neither slopes (P ≥ 0.103) nor intercepts (P ≥ 0.083) differed from one and zero, respectively. Fiber components appear to be suitable internal markers for measuring recoveries of DM following wetting, but this approach depends on complete recovery of shattered leaf particles before conducting laboratory analyses. USDA-ARS, U.S. Dairy Forage Research Center, 8396 Yellowstone Dr., Marshfi eld, WI 54449. Mention of trade names or commercial products is solely for the purpose of providing specifi c information about scientifi c procedures and/or subsequent evaluation of results and does not imply any recommendation or endorsement by the USDA. Received 4 Jan. 2008. *Corresponding author (wayne.coblentz@ars.usda.gov). Abbreviations: ADF, acid-detergent fi ber; ADFas, acid-detergent fi ber determined sequentially following initial extraction in neutral detergent containing both α-amylase and sodium sulfi te; ALF, proportion of alfalfa, in g kg−1; CELLas, cellulose determined sequentially following initial extraction in neutral detergent containing both α-amylase and sodium sulfi te; DM, dry matter; HEMIas, hemicellulose determined sequentially following initial extraction in neutral detergent containing both α-amylase and sodium sulfi te; LIGas, acid-detergent lignin determined sequentially following initial extraction in neutral detergent containing both α-amylase and sodium sulfi te; NDF, neutral-detergent fi ber without additives; NDFa, neutral-detergent fi ber with heat-stable α-amylase; NDFas, neutral-detergent fi ber with heat-stable α-amylase and sodium sulfi te; NDFs, neutral-detergent fi ber with sodium sulfi te. Published in Crop Sci. 48:2481–2489 (2008). doi: 10.2135/cropsci2008.01. 0006 © Crop Science Society of America 677 S. Segoe Rd., Madison, WI 53711 USA All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.