Cell-Constituents, Tannin Levels by Chemical and Biological Assays and Nutritional Value of Some Legume Foliage and Straws

Twenty six straw and 15 foliage samples of Lathyrus sativus,Vicia narbonensis,V sativaandV erviliawere analysed for ash, crude protein (CP), neutral detergent fibre (NDF), acid detergent fibre (ADF), extractable phenols (Pe), extractable tannins (Te), extractable condensed tannins (CTe), protein precipitation capacity (PPC) andin vitrocharacteristics predicted from Hohenheim gas test. The content of crude protein in the foliage was significantly higher than that of the straws (152·6 vs 64·5 g kg−1), while ash (82·8 vs 116·8 g kg−1), NDF (332·7 vs 523·5 g kg−1) and ADF (205·2 vs 369·9 g kg−1) were significantly lower. For straws ofL sativus,V narbonensisandV sativa, there was no significant difference in the protein and ADF contents, whereas ash and NDF contents were significantly lower and higher respectively inL sativusas compared toV narbonensisorV sativa. Predicted from gas volumes, the organic matter digestibility (OMD: 70 vs 56%) and metabolisable energy (ME: 9·7 vs 7·3 MJ kg−1) were significantly higher for the foliage compared to straws. The OMD ofL sativusstraws was significantly lower compared to the straws ofV narbonensisandV sativa. The OMD and ME of the straws of second year was significantly lower than those of the first year. The CP, OMD and ME ofV sativafoliage were higher than that ofV narbonensis. There was no difference in the cell constituents, OMD and ME of foliage samples ofV sativaharvested in May 1992 and June 1992. The contents of Pe, Te and CTe of straws were 1·08%, 0·43% and 0·33%, respectively, and those of foliage were 2·27%, 1·30% and 1·63%, respectively. PPC was not detected for any of the foliage and straw samples. The results suggested that the tannin levels of legume straws investigated are negligible and those of the legume foliage are very low. This does not appear to adversely affect their nutritive value since the maximum decrease in OMD by the tannins was about 3% units.