Effect of drying method and condensed tannin on detergent fiber analysis of sericea lespedeza

The effect of forage drying method on interrelationships between condensed tannins and fiber as determined by the detergent system of analysis was studied in a randomized block field experiment with three cultivars of sericea lespedeza ( Lespedeza cuneata ) (Dum‐Cours) G Don). Harvested forage was ovendried and freeze‐dried, and neutral detergent fiber (NDF) was determined with and without sodium sulfite added during the extraction. Acid detergent fiber (ADF), permanganate lignin, cellulose, and acid detergent insoluble nitrogen (N) were determined by separate and sequential ADF analyses. Without sodium sulfite, oven‐drying, compared with freeze‐drying, increased NDF, neutral detergent insoluble N, and sequentially‐analyzed ADF and lignin, due to precipitation of condensed tannins and protein in neutral detergent. Acid detergent fiber, lignin, and acid detergent insoluble N were higher in sequentially‐analyzed oven‐dried and freeze‐dried forages, compared with separate‐sample analyses, with a greater effect in oven‐dried samples. Neutral detergent fiber of both oven‐dried and freeze‐dried samples contained tannin‐protein complexes (precipitants), with more occurring in oven‐dried samples. When sodium sulfite was included in the neutral detergent extraction, all drying treatment differences in NDF, neutral detergent insoluble N, ADF, acid detergent insoluble N, and lignin were removed. Sequential NDF‐ADF analysis with sodium sulfite is recommended to minimize influence of condensed tannin on the detergent fiber system for sericea lespedeza.