|Jung, Hans Joachim|
|Rock, K - UNIVERSITY OF MINNESOTA|
Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: March 15, 2009
Publication Date: July 12, 2009
Citation: Jung, H.G., Rock, K.P., Lamb, J.F. 2009. Forage Quality of Biomass vs. Conventional Alfalfa Cut at Early Bud or Late Flower Maturity [abstract]. Journal of Animal Science. 87(E-Supplement):545. Technical Abstract: Cellulosic bioenergy systems will result in large areas planted to biomass crops. An important question is whether biomass crops can also be used for livestock feed. This study compared forage quality of an experimental alfalfa germplasm developed for a biomass production system with a conventional variety when harvested at early bud (four times annually) and late flower (three times annually) maturity stages. Replicated field trials were established at two locations and harvested in 2007 and 2008. Leaf percentage and stem NDF, ADL, and 16- and 96-h in vitro rumen NDF digestibility (IVNDFD) were determined. As expected, delaying harvest to late flower reduced leaf percentage (56.5 vs. 46.7%), increased stem NDF (58.7 vs. 65.9% DM) and ADL (16.0 vs. 16.7% NDF) concentrations, and reduced stem 16-h (22.0 vs. 20.0%) and 96-h (55.5 vs. 50.8%) IVNDFD. When harvested at early bud, biomass alfalfa had less leaf material (55.6 vs. 57.4%) and a lower stem ADL concentration (15.9 vs. 16.0% NDF), was lower in stem fiber digestibility (21.8 vs. 22.1% and 55.4 vs. 55.7% for 16- and 96-h IVNDFD, respectively), and had a higher stem NDF concentration in the first (58.3 vs. 55.7%) and last (61.3 vs. 59.4%) harvests, but not the two mid-summer harvests. Harvesting at late flower, biomass alfalfa again had a lower leaf percentage (44.3 vs. 49.2%) and stem ADL concentration (16.6 vs. 16.8% NDF). Stem NDF concentration of the biomass alfalfa was higher (67.0 vs. 64.7% DM) for all three late flower harvests. Stem fiber digestibility was lower for biomass alfalfa at two of three harvests, the first (19.9 vs. 20.7% and 49.6 vs. 51.1% for 16- and 96-h IVNDFD, respectively) and last (19.1 vs. 19.6% and 49.2 vs. 50.3% for 16- and 96-h IVNDFD, respectively). When harvested at late flower for biomass, both alfalfa types were of low quality. Although quality of the biomass alfalfa was lower than the conventional variety, the reductions were minor if harvested at early bud. Producers will have some flexibility in how they manage and utilize biomass alfalfa varieties.