Effect of Drying Method and Fiber Analysis Methodology on Fiber Concentration of Texas Legumes Containing Condensed Tannins.

This study was conducted to determine whether drying method and detergent fiber analysis methodology affect measured cell wall concentrations of Lespedeza stuevei, Desmodium paniculatum, and Acacia angustissima var. hirta, which contain high (225 g kg^-1), medium (139 g kg^-1) and low (33 g kg^-1) concentrations of total condensed tannins (TCT), respectively.  Collected leaves were oven dried (OD) or freeze dried and then analyzed for neutral detergent fiber (NDF)  with or without the addition of sodium sulfite to the NDF solution, followed by acid detergent fiber (ADF) using separate samples (ADFSEP) or sequential NDF-ADF (NDF-ADF SEQ) analysis using the fritted glass crucible method.  In addition, residues from ADFSEP and NDF-ADF SEQ were used to determine acid detergent insoluble nitrogen (ADIN).  Drying method, addition of sodium sulfite to NDF solution, and method for detergent fiber analysis had variable effects on cell wall components values that were species dependent. For the species with high and medium CT concentrations, sequential NDF-ADF analysis with addition of sodium sulfite reduced fiber residue contamination, regardless of the drying method. Higher ADIN values were observed when samples were OD, which could be associated to heat damage or nitrogen precipitation with CT.  For evaluation of fiber concentrations (sequentially) from plant materials containing CT, the addition of sodium sulfite appears to be more important than the drying method when using the fritted glass crucible method.