Nutrient intake and utilisation by goats fed dried leaves of the shrub legumes Acacia angustissima, Calliandra calothyrsus and Leucaena leucocephala as supplements to native pasture hay

Thirty-six indigenous goats were used to determine the potential of sun-dri ed leaves of the shrub legumes Acacia angustissima, Calliandra calothyrsus and Leucaena leucocephala as supplements to native pasture hay (NPH). The d ried leaves were included at the rates of 80, 160 and 320 g/head/ day. Cott onseed meal fed at the same levels, and NPH fed alone were included as cont rols. Among the browses, C. calothyrsus had the lowest N content of 19.0 g/ kg dry matter (DM) and A. angustissima the highest of 35.0 g/kg DM. The lea ves from the legumes had significantly less N and higher cell wall, neutral detergent insoluble N (NDIN) and acid detergent insoluble N (ADIN) content s than cottonseed meal. The values of NDIN as a fraction of total N were 19 , 456, 526 and 816 g/kg for cottonseed meal, L. leucocephala, A. angustissi ma and C. calothyrsus, respectively. Proanthocyanidin contents were 33, 196 and 134 g/kg DM for A. angustissima, C. calothyrsus and L. leucocephala, respectively. Type of supplement did n ot affect (P > 0.05) NPH, total and digestible DM intakes although NPH inta ke was depressed (P < 0.05) at the highest level of supplementation compare d to the first two levels. Animals fed legumes excreted significantly more (P < 0.001) faecal N (g/kg N intake) than animals consuming cottonseed meal . The reverse was observed for urine N. Among the legumes, C. calothyrsus h ad significantly higher (P < 0.001) N in faeces (958 g/kg N intake) than A. angustissima (630) and L. leucocephala (615). Significant (P < 0.05) corre lation coefficients were obtained between proanthocyanidins (PAs) intake an d faecal N, NDIN and ADIN (0.535, 0.501 and 0.786, respectively). Regressin g digestible N on N intake indicated that A. augustissima and C. calothyrsu s tannins had significant effects on the digestion of dietary N. The animal responses were discussed in relation to PAs content. It was concluded that both the type and level of PAs were important determinants of the animal r esponses. (C) 2001 Published by Elsevier Science B.V.