Rapid Estimating Rumen Digestibility of Forage with Lignin Structures Based on Fourier-Transform Infrared Spectroscopy

Abstract

The experiment was aimed to predict the relationship between rumen degradation parameters and chemical composition, especially acid detergent lignin, and molecular structure profiles of lignin (the relative content ratio of syringyl and guaiacyl unit) of twenty-two herbaceous and leguminous forage, which were commonly used as roughage for dairy cows in the northeast of China. Analyses of the spectra of forage materials' high boiling solvent lignin samples showed that common features and specific vibrations to each unique lignin were found in the spectrum. In this paper, the spectra of materials high boiling solvent lignin demonstrated absorption at the band around 1332 cm–1 (syringyl) and 1258 cm–1 (guaiacyl). The spectra indicated that the lignin of the plant materials used in this study are H-G-S type. A broad range was found among the chemical composition for each feedstuff. The degradation kinetics characteristics among feedstuffs also had relatively large range of variation. The relative content ratio of syringyl (S) and guaiacyl (G) unit of leguminous samples positively correlated with some rumen degradation characteristics. However, there was no correlation between relative content ratio of S and G unit and degradation parameters among the herbaceous materials (p > 0.05). According to analyses, content acid detergent lignin (ADL) and relative content ratio of S and G could be the predictors of the degradation parameters expect SCP among forage. In conclusion, the relative content ratio of S and G might be potentially used to predict some of the degradation parameters (Kd CP, EDCP, SNDF) of leguminous feedstuffs.