RELATIONSHIPS BETWEEN PREFERENCE, RUMEN DEGRADABILITY, GAS-PRODUCTIONAND CHEMICAL-COMPOSITION OF BROWSES

The aim of this work was to assess whether degradability, gas producti on or chemical constituents could predict the preference of browses. F orty tropical browse species leaves with a crude protein (CP) content ranging from 79 to 307 g kg(-1) DM were used for this study. The neutr al detergent fibre (NDF) ranged from 220 to 694 g kg(-1) DM, while aci d detergent fibre (ADF) ranged from 146 to 523 g kg(-1) DM. The NDF-bo und nitrogen (NDFN) and ADF-bound nitrogen were particularly high in C alliandra calothyrsus, Acacia polyacantha, Sesbania sesban, Acacia ven osa and Acacia hockii. High levels of tannins were observed in Acacia species especially A. dolichocephala, A. hockii, A. microbotrya and A. salicina. High levels were also observed in Flemingia macrophyla and Leucaena pallida. The browse species differed (P < 0.05) in DM in sacc o degradability coefficients. High potential degradability (PD) and ef fective degradability (ED) were observed in Sesbania spp, Moringa sten opetala, Indigofera arrecta, Chamaecytisus palmensis and Atriplex spp. The browses differed (P < 0.05) in asymptotic gas (A(g)) production ( ml g(-1) OM), but had similar (P > 0.05) times of incubation at which half of the asymptotic gas had been formed. Preference and DM intake w ere positively correlated (P < 0.01) to NDFN, but negatively correlate d (P < 0.05) to NDF and ADF. The PD and A(g) were negatively (P < 0.00 1) related to NDF, ADF and lignin. Total phenols (TP) and condensed ta nnins (CT) were negatively (P < 0.05) related to PD, ED and A(g). A po sitive correlation was observed between CT and NDF-bound condensed tan nins (r = 0.55, P < 0.001) and, CT and TP (r = 0.40, P < 0.01). Predic tion equations were poor for DM intake and preference, moderate for ga s production and good for potential and effective degradabilities. The phenolic components were more related to dry matter degradation and g as production than to preference and dry matter intake. NDFN and A(g) made a positive contribution to both preference and DM intake. It was concluded that chemical constitutes such as N, NDF, NDFN, ADF and lign in are essential to predict the nutritive value of browses.