NITROGEN PARTITION IN CELL STRUCTURES OF TROPICAL BROWSE PLANTS COMPARED WITH TEMPERATE FORAGES - INFLUENCE ON THEIR IN-SITU DEGRADATION PATTERN

The N ruminal degradation of tropical browse plants was compared with that of forages harvested in temperate regions, and the relationships between in situ N degradability and detergent fibre N content examined . Six browse plants were collected during the hot dry season in the se mi-arid zone of West Africa (Senegal). Six hays were prepared from for ages grown at Clermont-Ferrand, a semi-mountainous area in a temperate zone. We measured the partition of nitrogen (N) in feedstuffs with th e detergent fibre system and the N and fibre N ruminal degradation wit h the nylon bag technique. Nitrogen in the neutral detergent fibre (ex pressed as percent total N) varied from IO to 64% for browses and from 23 to 48% for bays. For browses, an important part of the cell wall N was located in the acid detergent fibre (ADFN). As a consequence of t hese chemical composition variations, there were large differences in N degradability of the browses, from 28% (leaves of Guiera senegalensi s) to 86% (pods of Acacia raddiana). It was closely related to ADFN co ntents (RMSE= 3.6; R(2)=0.98). The extent of N degradability variation s was much lower for bays, from 70 to 79%.