Effect of slower nitrogen releasing additive on the quality of napiergrass(Pennisetum purpureum Schumach.) silage

Urea is commonly used as a feed additive to improve the quantity of nitroge n (N) and digestibility in ruminants. Supplementation of urea increases cru de protein but decreases the fermentation quality of silage with increasing pH by releasing ammonia N. Thus, oxalic acid diamide (oxamide, O) and guan yl urea sulfate (GU), N slow-release compounds, were used as additives in t he present study. As much as 650 grams of the napiergrass were ensiled into a laboratory silo (1.0 liter polyethylene container). The treatments were: no additive (control), O, O+glucose (OG), GU and GU+glucose (GUG). O and G U were added at the level of 0.23% N on the napiergrass fresh weight basis, and glucose was added at 1%. Silage was incubated for 7, 15, 30 and 60 day s at room temperature (28 degreesC). After the silo was opened, pH, content s of dry matter, total nitrogen (TN), volatile basic nitrogen (VBN) and org anic acids were determined. Compared with the control, OG, GU and GUG treat ments significantly decreased pH value, VBN/TN, acetic acid and butyric aci d contents, and significantly increased contents of dry matter, TN and lact ic acid after 60 days of fermentation. The length of storage did not affect dry matter, lactic acid and TN contents and VBN/TN. In conclusion, without glucose addition GU may be a good N supplement for silage making of napier grass, but glucose is necessary to improve fermentation quality when ensile d with O additive.