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

Abstract

Twenty six straw and 15 foliage samples of Lathyrus sativus, Vicia narbonensis, V sativa and V ervilia were 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) and in vitro characteristics 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 of L sativus, V narbonensis and V sativa, there was no significant difference in the protein and ADF contents, whereas ash and NDF contents were significantly lower and higher respectively in L sativus as compared to V narbonensis or V 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 of L sativus straws was significantly lower compared to the straws of V narbonensis and V 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 of V sativa foliage were higher than that of V narbonensis. There was no difference in the cell constituents, OMD and ME of foliage samples of V sativa harvested 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.