Lignin and Etherified Ferulates Affect Digestibility and Structural Composition of Three Temperate Perennial Grasses

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 to 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 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 and independence between Klason lignin and etherified ferulates. 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 multitrait differentiation. Future studies should be refocused on the use of acid detergent lignin, 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.