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Agronomy Journal Abstract -

Relationship between Fibrous Components and In vitro Dry Matter Digestibility of Autumn-saved Grasses1


This article in AJ

  1. Vol. 69 No. 4, p. 610-612
    Received: Jan 31, 1976

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  1. K. A. Archer and
  2. A. M. Decker2



Chemical techniques for the determination of cell wall constituents and cell contents have been developed which provide relatively quick, convenient methods for predicting the digestibility of forage samples. These purely chemical laboratory methods may not be as reliable as in vivo or in vitro techniques for forage quality evaluations but they do not require the maintenance of digestion stalls or fistulated animals. There is a needfor a better understanding of the relationships between chemical determinations and the actual feed value of forage samples. The specific objective of this paper was to investigate the relationship between in vitro dry matter digestibility and chemical analyses of cell walls and cell contents for evaluating the digestibility of autumn-saved forage grass samples.

Forage samples of ‘KY-31’ tall fescue (Festuca arundinacea Schreb.) and ‘Potomac’ orchardgrass (Dactylis glomerata L.), collected from two field experiments were used for these quality evaluations. These field experiments were designed to measure the influence of nitrogen fertilization and soil temperature on cell wall constituents and in vitro dry matter digestibility of previously unharvested fall accumulated growth sampled at early, medium and late fall dates. Samples were analyzed for neutral detergent fiber, acid detergent fiber, cellulose, hemicelouse, lignin and silica. In vitro digestable dry (IVDMD) matter was also determined for each forage sample.

Fiber, lignin, and silica contents of autumn-saved forage samples were all highly correlated with IVDMD, and equations were developed to predict IVDMD from these chemical constituents. The following summative equation is proposed for the calculation of IVDMD: IVDMD = 0.98 (100 − NDF) + NDF( 91.1 − 1.43 (LIG + SIL) / ADF)

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