Abstract: To evaluate effects of adding molasses and urea on the fermentation quality of napier grass (Pennisetum purpureum Schumach.) silage, napier grass harvested at 65 days (elongation stage) was ensiled in laboratory silos for 3, 7, 14, and 30 days at the ambient temperature. Four treatments included: no additives (control), 4% molasses (M), 0.4% urea (U), and 4% molasses+0.4% urea (MU). Samples were taken for analyzing fermentation quality after the silos were opened. Results showed that the control decreased fermentation quality during the later stage (14~30 d) of ensiling. The treatment U mainly produced acetic acid and butyric acid, and significantly increased pH and NH₃-N/total nitrogen values compared with control(P<0.05). Both treatment M and MU significantly increased water soluble carbohydrate and lactic acid contents (P<0.05), maintained a low level of butyric acid (<0.3 g穔g^-1 DM) and constantly kept high value of lactic acid/acetic acid over the fermentation process. In final silages, both treatment M and MU had significantly lower neutral detergent fiber and acid detergent fiber contents (P<0.05), and treatment MU had significantly higher crude protein content compared with control (P<0.05). In conclusion, adding 4% molasses or the combination of 4% molasses with 0.4% urea improved fermentation quality, which promoted degradation of structural carbohydrate, and the combination of 4% molasses with 0.4% urea increased crude protein content of napier grass silage.

Key words: Napier grass, Molasses, Urea, Fermentation quality

摘要： 为评价添加糖蜜和尿素对象草(Pennisetum purpureum Schumach.)青贮发酵品质的影响,试验设4个处理:即无添加(对照)、4%糖蜜组(M)、0.4%尿素组(U)、4%糖蜜＋0.4%尿素组(MU),添加比例以鲜重为基础。在青贮后第3,7,14,30 d开窖,取样分析其发酵品质。结果表明:对照发酵品质在青贮后期(14~30 d)下降;U组主要发酵产物是乙酸和丁酸,且pH和氨态氮/总氮值显著高于对照(P<0.05),发酵品质最差;M组和MU组水溶性碳水化合物和乳酸含量显著高于对照(P<0.05),保持高而稳定的乳酸/乙酸值和低的丁酸含量(<0.3 g·kg^-1 DM);与对照相比,仅MU组粗蛋白质含量显著提高(P<0.05),M组和MU组中性洗涤纤维和酸性洗涤纤维含量显著降低(P<0.05)。综上所述,单独添加4%糖蜜或与0.4%尿素组合添加均能提高象草青贮饲料的发酵品质,促进结构性碳水化合物的降解,组合添加4%糖蜜和0.4%尿素提高了象草青贮饲料的粗蛋白质含量。

关键词: 象草, 糖蜜, 尿素, 发酵品质