Fiber Digestion Dynamics of Sward Components within Switchgrass Populations

Authors

Daren D. Redfearn, Louisiana State UniversityFollow
Kenneth J. Moore, Iowa State University
Kenneth P. Vogel, University of Nebraska-LincolnFollow
Steven S. Waller, University of Nebraska-LincolnFollow
Robert B. Mitchell, Texas Tech UniversityFollow

Document Type

Article

Date of this Version

1999

Citation

Crop Sci. 39:784-789

Comments

U.S. government work

Abstract

Forage quality as it relates to plant maturity is well established; however, strategies for improving fiber digestion in switchgrass populations have not been determined. The objectives of this study were to determine fiber digestion of sward components within switchgrass (Panicum virgatum L.) populations and which aspects of fiber digestion dynamics caused in vitro dry matter disappearance (IVDMD) differences of six switchgrass populations. This study was conducted in 1993 near Ames, IA, and Mead, NE. The experimental design was a randomized complete block design with a split-plot arrangement of treatments with four replicates at each location. Whole plots were populations and subplots were sward maturity. ‘Trailblazer’, ‘Pathfinder’, ‘Cave-in-Rock’, and three experimental switchgrass populations were used in this study. Populations were harvested on 9 June, 19 July, and 27 August at Ames and on 10 June, 27 July, and 26 August at Mead. Fiber composition and digestibility were determined on leaf blade, leaf sheath, and stem fractions of the primary growth stages. Significant differences for theoretical true digestibility (TD) and neutral detergent fiber (NDF) existed for morphological components at each sward maturity. However, digestion characteristics of the sward components were not stable across primary growth stages. Rate of fiber digestion was faster for most sward components at Ames than Mead, although stems of elongating tillers from elongating swards digested faster on plants grown at Mead than Ames. Rate of fiber digestion of stems was typically slower than either leaf blades or sheaths, but in several instances they were similar or stems had faster rates of fiber digestion. Although phenotypic selection can increase fiber digestibility, plant maturity remains an important factor, and selections may require evaluation at different stages of morphological development. Thus, improvements in forage digestion, at least in switchgrass, may only be manifested for the growth stage at which it was selected.