Stem Morphological and Cell Wall Traits Associated with Divergent In Vitro Neutral Detergent Fiber Digestibility in Alfalfa Clones
2006
Jung, H. G. | Lamb, J. F. S.
Poor cell wall digestibility of alfalfa (Medicago sativa L.) stems limits available energy to ruminants. This study compared alfalfa clones identified as either low or high rapid (16 h), or low or high potential (96 h) stem in vitro neutral detergent fiber digestibility (IVNDFD) for stem detergent fiber, cell wall, and morphology traits. Clones were established in replicated field plots at two sites in Minnesota during 2001 and harvested twice (primary spring growth and first summer regrowth) in the two following years. Presence of flowers, stem length, internode number, mean internode length, and number of elongating internodes was determined on 10 stems from each plot at every harvest. Herbage was dried and the stem fraction was analyzed for 16- and 96-h IVNDFD, detergent fiber components, and cell wall concentration and composition (Klason lignin, individual neutral sugars, and total uronic acids). Stem neutral detergent fiber (NDF) and cell wall concentration were lower for the high rapid than low rapid IVNDFD clones, but the high and low potential IVNDFD clonal groups did not differ. Lignin and pectin concentrations of the cell wall were lower and higher, respectively, for both high IVNDFD groups than their corresponding low groups. The low rapid and high potential IVNDFD groups had longer stem and internode lengths than their corresponding groups.
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