Effect of ensiling density on fermentation quality of napiergrass (Pennisetum purpureum Schumach.) silage

The poor quality of silage of tropical grasses may related to the difficult y of excluding air at ensiling due to their high fiber content. The process es of respiration and proteolysis by plant enzymes during the early stages of ensiling are very important keys to make good quality silage. The aim of this experiment is to clarify whether the exclusion of air from the silage mass affects the quality of the napiergrass silage. Two plots of napiergra ss were cultivated: one was applied with nitrogen (N) at 50 kg/ha in April and the other was not applied with N, The first growth was harvested in Jul y and immediately chopped into about I em length. The treatments were high (77g/100ml), medium (63g/100ml) and low (49g/100ml) densities of ensiling. Napiergrass was ensiled into a laboratory silo and incubated for 6, 15 and 30 days at 25 degreesC. After opening the silo, pH, total nitrogen (TN), vo latile basic nitrogen (VBN) and organic acids were determined. No significa nt effects of N application were observed in all parameters tested except f or N content of silage. The pH value, acetic acid, butyric acid, VBN/TN sig nificantly (P <0.01) decreased in the high density silage, while lactic aci d increased. The pH value was increased by low density ensiling clue to hig her VBN/TN. In conclusion, high density ensiling into the silo could improv e the fermentation and nutritive qualities of napiergrass silage irrespecti ve of application.