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Location: Plant Science Research

Title: Gain from selection for 16- and 96-h in vitro NDF digestibility of alfalfa stems

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: 3/2/2011
Publication Date: 7/10/2011
Citation: Jung, H.G., Lamb, J.F. 2011. Gain from selection for 16- and 96-h in vitro NDF digestibility of alfalfa stems [abstract]. Journal of Dairy Science. 94(E-Supplement 1):233.

Interpretive Summary:

Technical Abstract: Alfalfa is a high-quality forage, but stems are high in NDF and of limited digestibility. A gain from selection study with alfalfa populations selected for divergent in vitro NDF digestibility (IVNDFD) was planted at St. Paul and Becker, MN. Two cycles of selection were conducted starting with a base population created by mixing seed from six commercial varieties. Individual plants (N=2,000) were harvested twice (spring and first regrowth) at late flower for 2 years. Plants consistently low or high for 16- or 96-h IVNDFD were crossed to create four cycle one IVNDFD populations: low 16-h/low 96-h (LL), low 16-h/high 96-h (LH), high 16-h/low 96-h (HL), and high 16-h/high 96-h (HH). Cycle one populations were planted and harvested twice annually for 2 years to identify plants with appropriate IVNDFD combinations and crossed to create cycle two populations. Near-infrared reflectance spectroscopy calibrations were developed for NDF, ADL, Klason lignin, cell wall polysaccharide components, and 16- and 96-h IVNDFD based on 470 samples from the base population, cycle two, and other experiments. Data were analyzed as a randomized complete block with four replicates, two locations and nine populations, and two harvests arranged as repeated measures. The least significant difference test (P < 0.05) was used to compare population means when the F-test was significant. After two cycles of selection, 16-h IVNDFD increased from 19.3% for the base population to 20.1% for the HH population. The LL population (19.0% 16-h IVNDFD) differed from the HH population after two cycles but not from the base. Both LL (50.3%) and HH (55.8%) differed for 96-h IVNDFD from the base (52.4%) after two cycles. The LH and HL populations did not differ significantly from the base; however, means shifted in the direction of the positive selection criterion. Selection for greater IVNDFD resulted in less NDF, cell wall, and lignin (ADL and Klason) in the cycle two HH than the base and cycle two LL populations. Cellulose and pectin increased for HH cycle two and hemicellulose declined in cycle two LL compared to the base. Genetic selection in alfalfa was successful in improving IVNDFD of stems.