The fibre fraction (= non-starch polysaccharides; NSP) of tropical forage legumes is a potentially important source of dietary energy. Such legumes, however often contain tannins which can reduce the fermentability of the NSP fraction. In this study, the monosaccharide composition and in vitro digestibility of the NSP fraction of eleven tropical forage legumes varying in condensed tannin content, were investigated.
Milled, lyophilised leaves of 5 species of forage legume from Ethiopia, Sesbania goetzei (SG), Sesbania sesban (SS) Leucaena leucocephala (LL), Acacia cyanophylla (AC), Chamaecytisus palmensis (CP)) and six from Colombia, Calliandra sp. 29400 (C), Dioclea guianensis (DG), Flemingia macrophylla 77409 (FM) Tadehagi sp. 23227 (T23), 13269 (T69) and 13275 (T75)) were used. One gram samples were fermented at 39°C for 7 d under anaerobic conditions in modified Van Soest medium inoculated with bovine rumen fluid (5 replicates per species). At the end of the fermentation period, residues were filtered, washed with distilled water and lyophilised. The NSP content and composition of the original samples and their residues were determined by the method of Englyst and Cummings (1984). The bound, soluble and total condensed tannin contents of the original samples were determined by the method of Terrill et al. (1992).