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Crop Science Abstract -

Divergent Selection for In Vitro Dry Matter Digestibility in Smooth Bromegrass1


This article in CS

  1. Vol. 26 No. 6, p. 1123-1126
    Received: June 19, 1985

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  1. N. J. Ehlke,
  2. M. D. Casler,
  3. P. N. Drolsom and
  4. J. S. Shenk2



Improving the nutritive value of smooth bromegrass (Bromus inermis Leyss.) is dependent on successfully selecting for traits that influence digestibility and intake. The objectives of this research were to evaluate the effects of divergent selection for in vitro dry matter digestibility (IVDMD) and to determine correlated responses to selection for cell wall constituents. Divergent selection for IVDMD was practiced in the Wisconsin experimental smooth bromegrass synthetic B8, resulting in two nine-clone first cycle synthetics, B8HD and B8LD. The B8, B8HD, and B8LD synthetics were seeded in May 1981 at Arlington, WI, in seven randomized complete blocks. In 1982 and 1983, forage samples were harvested at six spring and eight summer growth stages for the prediction of IVDMD, crude protein, and cell wall constituents using near-infrared reflectance spectrophotometry. In vitro dry matter digestibility decreased in the spring from 878 to 660 g kg−1 and in the summer from 804 to 658 g kg−1. Divergent selection responses were significant for IVDMD for all growth stages from late May through late August. Correlated divergent responses for acid detergent lignin (ADL) were significant for the same growth stages as IVDMD. Correlated selection responses for crude protein and all other cell wall constituents were never significant for more than three growth stages. Population ✕ year interactions tended to be nonsignificant. Selection responses indicated that ADL was the most limiting factor to IVDMD in B8. The nearly season-long improvement in IVDMD was indicative of nutritive value improvements to smooth bromegrass for hay or pasture.

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