PROMISING TROPICAL GRASSES AND LEGUMES AS FEED RESOURCES IN CENTRAL TANZANIA V - EFFECT OF SUPPLEMENTING CENCHRUS-CILIARIS HAY WITH LEAVES FROM 4 LEGUMES ON INTAKE AND DIGESTIBILITY BY GROWING MPWAPWA BULLS

In Trial 1, six growing Mpwapwa bulls (mean age 1.5 years, mean body w eight 158 kg) were used in a 6 x 6 Latin square design to study the ef fect on intake and digestion of supplementing Cenchrus ciliaris cv. Ko ngwa hay with four different legume leaf proteins. Hay alone and fish meal (FM) treatments were included as negative and positive control tr eatments, respectively. The grass hay was fed allowing above 40% refus al to maximize selectivity and contained 5.1% crude protein (CP), 76.1 % neutral detergent fibre (NDF), 9.9% lignin and 3.1% silica. The prot ein sources were dried leaves of Macroptilium atropurpureum cv. Siratr o (MAS), Macrotyloma axillare (MAA), Neonotonia wightii cv, Mpwapwa (N WM), Stylosanthes scabra cv. Seca (SSS) and FM. The protein sources we re fed aiming at supplying approximately 150 g CP/day. The legume CP c ontents varied from 18.6-20.6% and the FM contained 54.7%. In Trial 2 in a completely randomised block design, 8 bulls were used to measure the digestibility of the legumes alone. Selective feeding resulted in consumption of hay containing 6.2% CP. The apparent digestibility of o rganic matter (OM) and NDF were 58.3 and 62.5%, respectively. Suppleme nting the hay resulted in intake of a diet with CP ranging from 8.0-8. 5%, Despite the increased CP intake, neither the digestibility of OM n or NDF increased significantly, implying that the protein was not a fi rst limiting factor for fibre digestion. The grass hay OM intakes vari ed between 21.0 and 22.2 g/kg weight (BW) per day (77.3-86.0 g/kg BW0. 75/d) and were not improved by protein supplementation. Significant im provements (P < 0.001) in daily intakes of total OM and CP were observ ed by supplementation, although tod NDF was not improved. All protein supplements except MAS improved (P < 0.05) digestible OM intakes compa red to the unsupplemented hay. Calculated digestible and metabolizable energy values for the diets were nor improved by supplementation, How ever, an improvement in total energy and protein intake may be obtaine d as a result of supplementation, It is concluded that it is beneficia l to use MAA, NWM, SSS and also FM in C. ciliaris-based diets to impro ve total intake of CP by growing bulls. Total intake of OM and digesti ble OM may also be improved, bur the levels are only on the order of 1 0%. The use of legume supplements and allowing ample feed refusals may result in an estimated daily BW gain of 200-400 g. (C) 1998 Elsevier Science B.V.