Paper-Lecture27 - Kinetics of Cell-Wall Digestion of...

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Kinetics of Cell-Wall Digestion of Orchardgrass and Alfalfa Silages Treated with Cellulase and Formic Acid1,* E.M.G. NADEAU,*v3 D. R. BUXTON,*!4 E. LINDGREN,t and P. LlNGVALLt ‘Iowa State University, Ames 50011 tDeparlment of Animal Nutrition and Management, The Swedish University of Agricultural Sciences, 753 23 Uppsala. Sweden ABSTRACT The objectives of this study were to determine the effects of cellulase (from Trichoderma longibrachia- turn) combined with formic acid, applied before ensil- ing, on the subsequent concentration and composition of the cell wall and on the extent and rate of in situ cell-wall digestion of orchardgrass ( Dactylis glomer- uta L.) and alfalfa (Medicago sativa L.). Treated and control forages of both plant species were ensiled for at least 60 d before being ruminally digested by two fistulated cows. Analyses of NDF, ADF, and acid de- tergent lignin were conducted sequentially on original and digested samples. Data were fitted with a first- order, nonlinear model to estimate extents and rates of digestion of potentially digestible NDF, cellulose, and hemicellulose. The concentration of indigestible residue and the discrete lag time before digestion were also determined for the cell-wall components. After ensiling, the mean NDF concentration of treated silages was 19% lower than that of control silages; the effect was greater for orchardgrass than for alfalfa. The extent of digestion of NDF, cellulose, and hemicellulose, respectively, was 33, 37, and 27% lower for treated silages than for control silages. Treatment effects on the extent of digestion varied between plant species. Cellulose from treated or- chardgrass was digested 19% more slowly than cellu- lose from the control silage. Indigestible residue con- centrations of NDF, cellulose, and hemicellulose, Received July 24, 1995. Accepted April 23, 1996. 1Joint contribution of the Field Crops Research Unit, US Dairy Forage Research Center of USDA-ARS, and Iowa State University. Journal Paper Number 5-16455 of the Iowa Agriculture and Home Economics Experiment Station. Project Number 2709. 2Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product? and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable. 3Department of Agronomy. 4Address reprint requests to D. R. Buxton, USDA-ARS, 1577 Agronomy Hall, Iowa State University, Ames 50011. respectively, were 7, 8, and 7%’ lower in treated silages than in control silages. Thus, extensive cell- wall degradation by cellulase during ensiling resulted in less digestible cell-wall material for ruminal diges- tion but greater total cell-wall degradation, including that during ensiling and ruminal incubation, espe- cially during early digestion in the rumen. ( Key
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This note was uploaded on 09/19/2011 for the course ANS 5446 taught by Professor Brown during the Spring '08 term at University of Florida.

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Paper-Lecture27 - Kinetics of Cell-Wall Digestion of...

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