Location: Dairy Forage ResearchTitle: Lignin and etherified ferulates impact digestibility and structural composition of three temperate perennial grasses
|JUNG, HANS - Retired ARS Employee|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/2016
Publication Date: 3/3/2017
Citation: Casler, M.D., Jung, H. 2017. Lignin and etherified ferulates impact digestibility and structural composition of three temperate perennial grasses. Crop Science. 57:1010-1019.
Interpretive Summary: The livestock industry depends on the supply of new forage varieties with traits that help to optimize livestock production and profitability. Increased digestibility is one of the more potentially important of these traits. Two mechanisms to increase digestibility of grasses are: reduce lignin concentration or reduce the amount of chemical bonding between lignin and sugars in the plant cell wall. This study documented that both mechanisms can be effective, but that there are significant problems associated with reduced lignin. The laboratory method used to estimate lignin generated inconsistent results, so selection was not very reliable. This study concluded that breeding to reduce lignin should be based on a different chemical assay, while breeding to reduce the amount of chemical bonding between lignin and cell-wall sugars can proceed as planned. Both plant traits can be used as mechanisms to increase digestibility of grasses and should have positive impacts on grass breeding programs.
Technical Abstract: Breeding grasses for increased digestibility increases their value and profitability in ruminant livestock production systems. Digestibility can be improved in grasses by either increasing the concentration of soluble and readily fermentable carbohydrates or by altering the plant cell wall to create faster and more ready access to carbohydrates by rumen microbes. Two mechanisms to accomplish the latter are to decrease lignin concentration or decrease the frequency of lignin-ferulate covalent bonds. The purpose of this study was to quantify the relative impact of these two mechanisms on in vitro neutral detergent fiber digestibility (IVNDFD) for three forage grasses: orchardgrass (Dactylis glomerata L.), reed canarygrass (Phalaris arundinacea L.), and smooth bromegrass (Bromus inermis Leyss.). The selection scheme was designed to create divergence in both traits, Klason lignin and etherified ferulates, which were independent of each other. This was successful only in reed canarygrass, due to the strong positive genetic correlation between the two traits in the other two grasses. Repeatability of Klason lignin concentration was very low, which probably contributed to our inability to create the desired spectrum of multi-trait differentiation. Future studies should be refocused on the use of acid detergent lignin (ADL), which has shown a history of high repeatability and heritability. Repeatability of etherified ferulates was high for all three species, indicating that further genetic gains could be realized by selection for reduced etherified ferulate cross-linking within the cell walls of these grasses.