Livestock-Based Farming Systems, Renewable Resources and the Environment
The aim of this in vitro study was to evaluate the effect on methane production of potassium nitrate or urea as NPN sources in substrates containing varying ratios of sugar cane and Tithonia diversifolia. The treatments in a 6*2 factorial arrangements with 4 replications were: proportions of Tithonia leaf meal of 0, 20, 40, 60, 80 and 100% replacing sugar cane and source of NPN (Potassium nitrate or urea).
Gas production and substrate solubilized was increased with increasing proportions of Tithonia in the substrate. Methane percentage in the gas and methane per unit substrate solubilized was decreased with increasing proportion of Tithonia in the substrate. At all ratios of Tithonia and sugar cane the percentage of methane in the gas and the production of methane per unit substrate solubilized was reduced by nitrate compared with urea There were no differences in ammonia concentration but VFA concentration was increased as Tithonia replaced sugar cane in the substrate. Ammonia and VFA concentrations were lower with nitrate than with urea.