초록
To standardize proper formulation of urea and molasses, the former to increase crude protein content of tropical grass and the latter for improving its silage quality, we examined the fermentation quality of silage of fresh and wilted napiergrass (Pennisetum purpureum Schumach) with different levels of urea and molasses with or without lactic acid bacteria (LAB). Silage was made of napiergrass with conditions of fresh young (Exp. 1),young wilted for half day (Exp. 2) and fresh mature (Exp. 3). Chopped plant materials of about 1cm length were ensiled into a laboratory silo and incubated for one month at $25^{\circ}C$. The treatments were the combination of 0, 0.2 and 0.6% of urea and 0, 2 and 5% of molasses (fresh material basis) with or without LAB inoculation. After opening the silo, pH, organic acids, volatile basic nitrogen (VBN) and total nitrogen (TN) were determined. Addition of molasses significantly (p<0.01) lowered pH values in three experiments. Though molasses addition increased lactic acid production even at a higher level of urea, pH values at 0 and 2% molasses were significantly increased by urea in fresh and wilted young silages, but in fresh mature silage it occurred only when molasses was not added. VBN/TN at 0.6% urea were decreased significantly by the highest molasses in three experiments. Significant increases in TN by the increasing of urea addition were observed at all levels of molasses in wilted young and fresh mature silages. In conclusion, a combination of 5% molasses and 0.6% urea could improve the nutritive and fermentation qualities of napiergrass silage under young, wilting and mature conditions.