Impact of fertilizer types on the nutritive quality of two tropical grass species harvested at different stages of growth during wet season
Keywords:Manure, Panicum maximum, Andopogon tectorum, chemical composition, in vitro digestibility, ruminant
The use of inorganic fertilizers has been reported to have improved pasture productivity, however it has also attributed to soil toxicity, environmental pollution, mineral imbalance, and health hazards among many adverse effects. This made the adoption of organic fertilizers became best alternative to correct nutrients deficiencies in the soil due to their environmental friendly nature and less cost effectiveness. To investigate the comparative advantages of these two types of fertilizer, an experiment was conducted to evaluate the influence of fertilizer types on the nutritive quality of Panicum maximum var. Ntchisi and Andropogon tectorum harvested at 6 and 8 weeks during the wet season. The study was a factorial experiment (4 x 2 x 2), arranged in a split-split-plot design with three replicates. There were 16 treatments to include; fertilizer types (NPK, Aleshinloye organo-mineral fertilizer, poultry manure and control (no fertilizer)), grass species (Panicum maximum var. Ntchisi and Andropogon tectorum) and age at harvest (6 and 8 weeks). Fertilizer treatments were allotted to the main plots while grass species were allotted to sub-plots and again harvest age was allotted to sub-subplots. Sub-samples taken from harvested forage materials were oven dried, properly milled and analysed in the laboratory to determine proximate composition [crude protein (CP%), ash, ether extract (EE%)], fibre fractions [acid detergent fibre (ADF%), neutral detergent fibre (NDF%), acid detergent lignin (ADL%), Cellulose, and Hemicelluloses) and in vitro gas production. Fertilizer types significantly (P<0.0.5) affected ADF, hemicellulose, cellulose and methane (CH4). The grasses fertilized with NPK had the highest value (9.00mL) for CH4. Poultry manure (PM) fertilized grasses recorded the highest value for in vitro dry matter digestibility (IVDMD) (89.38%). Andropogon tectorum fertilized with PM harvested at 6 weeks recorded the highest value for IVDMD (93.00%) and the same grass fertilized with NPK, harvested at 6 weeks recorded the highest values (0.37 mL and 4.70%) for short chain fatty acid and metabolizable energy, respectively. Therefore, this study established that fertilizer applications had an influence on fibre fraction, methane and post-incubation parameters of the grasses investigated.