Chemical composition and gas production substrates of maize cobs treated with combinations of urea and wood ash

Abstract

Effect of treating maize cobs with a combination of urea and wood ash (WA) on chemical composition and in vitro gas production truly degraded substrate (TDS) were examined. The treatments were:1) 100U = (100% urea and 0% wood ash), 2) 75U25WA = (75% urea and 25% wood ash), 3) 50U50WA = (50% urea and 50% wood ash), 4) 25U75WA = (25 % urea and 75% wood ash) and 5) 0U0WA = (Untreated maize cobs). The concentrations were reconstituted as follows: 100U = 5 kg urea dissolved in 100 liters of water /200 kg maize cobs; 75U25WA = 3.75 kg urea mixed with 7.5 kg WA in 100 liters of water/200 kg maize cobs; 50U50WA = 2.5 kg urea mixed with 15 kg WA in 100 liters of water/200 kg maize cobs; 25U75WA = 1.25kg urea mixed with 22.5 kg WA in 100 liters of water/200 kg maize cobs; Untreated = 200 kg maize cobs mixed with 100 kg water. Chemical composition of samples were analyzed to determine dry matter (DM), organic matter (OM), ash, crude protein (CP), neutral detergent fibre (NDF), acid detergent fibre (ADF) and acid detergent lignin (ADL). The samples were then incubated in vitro for 6, 12, 24, 48 and 72 hrs and their DM degradation kinetics determined. It was observed that crude protein contents declined as urea is substituted with WA while the ash contents increased. Treatment 25U75WA had the highest reduction in both NDF and ADF (660 and 360 g/kg) compared to those of 100U (700 and 380g/kg) and 0U0WA (840 and 430 g/kg). In contrast treatment 25U75 had the highest neutral detergent soluble (340 g/kg) while 0U0WA had the least (160 g/kg).Treatment 25U75WA had the highest gas production (73.5ml per 0.5mg sample; P=0.0001) and TDS (70.53%) while 0U0WA had the least. Treatment 25U75WA also resulted in the highest microbial mass protein (MMP) (53.55 mg) while 0U0WA had the least (25.20 mg). Treatment 25U75WA had the highest efficiency of microbial mass protein (EMMP) and partitioning factor (PF) (23.68 and 2.883) while 0U0WA had the least (12.00 and 2.500). It was concluded that combinations of 25% urea and 75% WA in the treatment of maize cobs had beneficial synergic effect and improved its nutritive value compared to treating it with urea alone.