|Jung, Hans Joachim|
|Engels, F - WAGENINGEN UNIVERSITY|
Submitted to: Grassland International Congress Proceedings
Publication Type: Proceedings
Publication Acceptance Date: November 15, 2004
Publication Date: June 30, 2005
Citation: Jung, H.G., Engels, F.M., Lamb, J.F. 2005. Influence of internode length on degradabiity of lucerne stems. 20th International Grassland Congress Proceedings. p. 224. Technical Abstract: Preliminary observations of how deeply rumen microbes could degrade different tissues within alfalfa stem pieces indicated a two-fold range among stem samples. Studies were undertaken to determine if extent of cell wall degradation in alfalfa was influenced by length of stem internodes. The seventh stem internode was collected after four wk of regrowth from a single alfalfa clone. Five short (20±1 mm) and six long (53±4 mm) internodes were selected, and 18- to 20-mm pieces excised. Stem pieces were coated with wax and the wax was removed at one end. After incubation with rumen fluid for 24 h, serial sections were made from the exposed end of the stem pieces and evaluated to determine depth of degradation for various tissues. In a second study, 20 alfalfa clones selected for low or high 16- or 96-h in vitro neutral detergent fiber degradability (IVNDFD) were grown in three field environments, sampled twice at flowering for 2 years, and evaluated for IVNDFD and internode length. Maximal depth of degradation of non-lignified tissues (collenchyma and parenchyma) was greater for stem pieces derived from longer internodes. For lignified tissues, only phloem fibers were degraded to greater depth when internodes were longer. Alfalfa clones selected for high 16-h IVNDFD had shorter average internode length than did low 16-h IVNDFD selections, whereas the opposite result was found for high vs. low 96-h IVNDFD selections. The low IVNDFD alfalfa selection groups were lower in degradability than the corresponding high groups. Tissues degraded within 16 h were primarily limited to those that are non-lignified. Degradation of alfalfa stem tissues is impacted by both internode length and lignification.