Influence of nitrogen fertilization and stage of maturity of mottgrass (Pennisetum purpureum) on its composition, dry matter intake, ruminal characteristics and digestion kinetics in cannulated buffalo bulls

Four ruminally cannulated buffalo bulls (300 kg) were fed mottgrass diets u sing a 4 x 4 Latin-square design. Treatments consisted of mottgrass fertili zed with 0 or 110.4 kg N/ha and harvested at 40 (ECM) and 60 (LCM) days. Fe rtilization increased the concentrations of crude protein (CP) and fibre co ntents. The CP contents of the mottgrass decreased and fibre contents incre ased with advancing maturity. Intake of dry matter (DM), organic matter (OM ), CP, neutral detergent fibre (NDF) and acid detergent fibre (ADF) were hi gher in buffalo bulls fed ECM than those fed LCM. The concentrations of tot al ruminal volatile fatty acids (VFA) and acetate were higher in animals fe d ECM than those fed LCM. In situ DM and NDF digestibilities of ECM were hi gher than those of LCM. However, DM and NDF digestibilities of ECM remained unaltered by N fertilization. The rates of DM and NDF disappearance of ECM were faster than those of LCM. However, N fertilization did not affect the DM and NDF rates of disappearance. In situ lag time of DM and NDF digestio n were shorter for ECM than those for LCM but no effect was noted due to N fertilization. The digestion extent of DM and NDF at 96 h was affected by m aturity, However, N fertilization did not have any effect. The digestibilit ies of DM, OM, CP, NDF and ADF were higher in buffalo bulls fed ECM than th ose fed LCM. However, the N fertilizer did not affect digestibilities of th ese nutrients. In conclusion, the N fertilization increased the CP concentr ation of the mottgrass but could not reverse the ill effect of maturity on the quality of mottgrass. (C) 1999 Elsevier Science B.V. All rights reserve d.