PROMISING TROPICAL GRASSES AND LEGUMES AS FEED RESOURCES IN CENTRAL TANZANIA - VI - NITROGEN-BALANCE IN GROWING BULLS CONSUMING TROPICAL HERBACEOUS FORAGE LEGUMES

Nitrogen balance was measured in six growing Mpwapwa bulls (mean age 1 .5 years, weight 131 kg) fed Cenchrus ciliaris hay and cassava as basa l diet (negative control) supplemented with dried leaves from four her baceous legumes: Macrotyloma axillare cv. Archer(MAA), Stylosanthes sc abra cv. Seca (SSS) and Neonotonia wightii cv. Mpwapwa (NWM); or with Fish meal (FM) as positive control in a 6x6 Latin square design. All t reatments with protein were formulated to provide the same energy and protein levels of intake. The digestible organic matter intakes were 1 3.9, 13.6, 14.2, 13.8 and 13.6 g per kg body weight (BW) per day in tr eatments supplemented with MAA, SSS, FM and NWM respectively and these were similar(P > 0.05) but significantly higher (P < 0.05) compared t o the negative control. The crude protein contents of the DM consumed ranged from 8.6 to 9.5% among the supplemented diets and these were hi gher than the unsupplemented treatment of only 3.9%. Nitrogen intake, faecal nitrogen output, urinary nitrogen output and nitrogen balance w ere significantly higher (P < 0.001) ir. the supplemented diets compar ed with the negative control. For the negative control treatment, nitr ogen balance was 0.09 g per kg W-0.75 whereas N balance ranged from 0. 19-0.32 g per kg W-0.75 in the other treatments. The ranking was: FM > SSS > MAS > MAA > NWM but they were not significantly different from each other. Only when calculated as percent N retained, was FM superio r to NWM (P < 0.05). It is concluded that using leaves from these legu mes as protein supplements will have an effect on N balance in growing Mpwapwa bulls comparable to fish meal. (C) 1998 Elsevier Science B.V. All rights reserved.