Location: Wheat, Sorghum and Forage ResearchTitle: Switchgrass biomass composition traits and their effects on its digestion by ruminants and bioconversion to ethanol
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/15/2016
Publication Date: 1/19/2017
Publication URL: http://handle.nal.usda.gov/10113/5729148
Citation: Vogel, K.P., Casler, M.D., Dien, B.S. 2017. Switchgrass biomass composition traits and their effects on its digestion by ruminants and bioconversion to ethanol. Crop Science. 57(1):275-281. https://doi.org/10.2135/cropsci2016.07.0625.
Interpretive Summary: Six generations of divergent breeding in switchgrass for increased or decreased forage digestibility using a laboratory digestion procedure known as in vitro dry matter digestibility or IVDMD resulted in significant changes in 20 biomass composition traits in the switchgrass strains developed by the breeding work. In this study, a statistical procedure known as multiple regression was used to determine which of the switchgrass biomass composition variables that were changed by the breeding work had the greatest effect on improving forage digestibility and ethanol yields if the biomass was used in a biorefinery. Ethanol yields and IVDMD were highly correlated. The biomass composition factors that had the greatest impact on both forage digestibility and ethanol yield were compounds that link biomass cell wall complex sugars to cell wall lignin. The IVDMD test, which acted as a biological selection index in the long-term breeding program, impacted an array of switchgrass biomass composition traits whose relative effects on both IVDMD and ETOH had not been previously quantified. The results also demonstrated that the IVDMD test can be used in breeding programs to improve both forage quality or ethanol yield of grasses grown for forage or bioenergy.
Technical Abstract: Six generations of divergent breeding in switchgrass (Panicum virgatum L.) for forage in vitro digestibility (IVDMD) resulted in significant changes in 20 biomass composition traits. Stepwise multi-regression was used to determine which of the 20 composition traits had largest significant effects on forage IVDMD and potential ethanol yield (ETOH) in a biorefinery. Switchgrass biomass samples from a field nursery containing the divergent switchgrass populations and families were harvested after flowering, dried, ground, and analyzed for composition traits by near infrared reflectance (NIRS) analyses using previously developed NIRS calibrations. After non-significant variables were eliminated, the resulting multiple regression models were highly significant (P< 0.001) and accounted for 95% of the total variation for both IVDMD and ETOH. Standardized partial regression coefficients were used to make estimates of the relative importance of each significant variable. The biomass composition factors that had the largest impact on both IVDMD and ETOH were esterified ferulates, p-coumarate esters (PCA), specific cell wall sugars that are involved in the linkage of cell wall lignin to hemicellulose, N, and extracted fats. Klason lignin was not a significant variable in either regression analysis even though it was strongly negatively correlated with both IVDMD and ETOH. The IVDMD test, which acted as a biological selection index in a long-term population breeding program, impacted an array of switchgrass biomass composition traits whose relative effects on both IVDMD and ETOH had not been previously quantified.