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Title: DIFFERENCES IN MORPHOLOGICAL AND CELL WALL TRAITS OF ALFALFA PLANTS SELECTED FOR DIVERGENT STEM IN VITRO FIBER DIGESTIBILITY

Author
item Jung, Hans Joachim
item Lamb, Joann

Submitted to: Joint Abstracts of the American Dairy Science and Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: 2/22/2006
Publication Date: 7/1/2006
Citation: Jung, H.G., Lamb, J.F. 2006. Differences in morphological and cell wall traits of alfalfa plants selected for divergent stem in vitro fiber digestibility [abstract]. Journal of Dairy Science. 89(Supplement 1):101.

Interpretive Summary:

Technical Abstract: 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 fiber, cell wall, and morphology traits. Five clones of each selection group were grown in replicated field plots at two locations. Primary spring growth and first summer regrowth were harvested in 2002 and 2003. Data were averaged across growth environments and harvests because interactions with alfalfa selection groups were non-significant. As expected, the high rapid clonal group was greater for 16-h IVNDFD than the corresponding low rapid clonal group. Similarly, the high potential clonal group was greater than the low potential clonal group for 96-h IVNDFD. Comparing the low and high rapid clonal groups, NDF and cell wall concentrations were lower for the high clonal group, but ADL and Klason lignin concentrations were only marginally different. Cell wall pectin concentration was greater in the high rapid clonal group. In contrast, NDF and cell wall concentrations were not different between the low and high potential clonal groups, but both ADL and Klason lignin were substantially lower for the high potential clonal group than the corresponding low clonal group. Stem lengths were longer for the low rapid and high potential clonal groups than their corresponding clonal groups, and all clonal groups had similar numbers of stem internodes. Mean internode lengths were greater for the low rapid and high potential clonal groups than their corresponding clonal groups. Our results indicate that rapid IVNDFD of alfalfa stems was associated with reduced cell wall concentration, increased cell wall pectin, and short internodes. High potential IVNDFD of alfalfa stems was a result of reduced cell wall lignification and long internodes. These observations can be reconciled with microscopic observations of how alfalfa stem tissues are digested by rumen microbes.