Author
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CASLER, MICHAEL - UNIVERSITY OF WISCONSIN |
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Jung, Hans Joachim |
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Submitted to: Crop Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 4/5/1999 Publication Date: N/A Citation: N/A Interpretive Summary: Grasses are the major feed resource for beef production and are becoming more important as dairy farmers switch back to grazing systems. While grasses and grazing offer environmental benefits that make livestock production more sustainable, the lower digestibility of grasses compared to grains limits milk and meat production. Development of improved grass varieties with increased digestibility of the fiber fraction is needed in order to provide the animal productivity needed to keep these sustainable farming systems economically viable. We have demonstrated that digestibility of fiber can be improved in smooth bromegrass by selection for reduced lignin (a part of fiber that limits digestibility) or reduced cross-linking of lignin to the carbohydrates in fiber. Because these two limits to digestibility were found to have independent effects on digestibility, simultaneous selection for both less lignin and less cross- linking should provide even better grass varieties than selection for either factor alone. These results have provided a beginning for the breeding of improved smooth bromegrass varieties and the same technology should be applicable to other grasses. Technical Abstract: Lignin and etherified ferulic acid (EthFA) are cell wall constitutes believed to have important negative impacts on digestibility of forage cell walls. Our objective was to identify genotypes of smooth bromegrass (Bromus inermis Leyss) with unconfounded divergence in lignin and EthFA, such that their independent effects can be determined on in vitro fiber digestibility y(IVFD). Eight clones were selected from each of four populations (Alpha, WB19e, Lincoln, and WB88S). Selection was successful for EthFA in all populations except WB88S, creating repeatable divergence of 11.2 to 12.5%. Selection was unsuccessful for lignin concentration per se, most likely due to large genotype x environment interactions. Nevertheless, the resulting clones showed significant variation for both EthFA and lignin concentrations, and these two variables were nearly independent among the selected clones. Both lignin and EthFA had significant negative effects on 96-hr IVFD, regardless of the statistical estimation method used. Across estimation methods, there was not a clear difference in the magnitude of the lignin and EthFA effects on IVFD. Both the total amount of lignin in the cell wall and the amount of ferulic acid cross-linking lignin to polysaccharides via ether bonds appear be under genetic control, and both components play a role in regulating the genetic potential for rumen degradation of cell walls in smooth bromegrass. These clones are a potential tool for conducting animal feeding trials using forages with relatively unconfounded differences in a single cell wall characteristic. |
