Abstract: To evaluate effect of adding formic acid on fermentation quality of napier grass (Pennisetum purpureum Schumach.), it was ensiled in laboratory silos for 0.5, 1, 2, 3, 5, 7, 14, and 30 days at the ambient temperature. The formic acid was added at levels of 0 (control), 2.2, 4.4 and 6.6 mL穔g^-1 on fresh weight basis, respectively. Samples were taken for analyzing fermentation quality after the silos were opened. Results showed that control attained a good fermentation quality with no butyric acid produced. Compared with the control, formic acid addition quickly acidified napier grass silage, and significantly increased water soluble carbohydrate content (P<0.05), and the effects increased as the addition volume increased. NH₃-nitrogen/total nitrogen of silage treated with 2.2 mL穔g^-1 formic acid increased rapidly after 2 days of ensiling and significantly higher than control after 3 days (P<0.05), and butyric acid began to be detected from d 7 of ensiling. There were no lactic acid and volatile fatty acids produced and the lowest NH₃-N/total nitrogen value (<12 g穔g^-1 TN) in both silages treated with 4.4 and 6.6 mL穔g^-1 formic acid. In conclusion, adding 2.2 mL穔g^-1 formic acid had a decreasing acidification which lowered the fermentation quality and nutritive value in the later ensiling period, whereas adding 4.4 mL穔g^-1 formic acid was sufficiently high to effectively conserve nutrients of napier grass.

Key words: Napier grass, Formic acid, Ensilage, Fermentation quality

摘要： 为评价甲酸对象草(Pennisetum purpureum Schumach.)青贮发酵品质的影响,分别设置添加量为0(对照),2.2,4.4和6.6 mL·kg^-1FM处理,在青贮0.5,1,2,3,5,7,14,30 d开窖,测定青贮饲料发酵品质的动态变化。结果表明:对照发酵品质良好,未见丁酸生成;与对照相比,添加甲酸能够快速酸化青贮饲料,明显提高水溶性碳水化合物含量(P<0.05),且添加量越高效果越好;添加2.2 mL·kg^-1甲酸组氨态氮/总氮值在2 d后快速升高,且在3 d后显著高于对照(P<0.05),并从第7 d开始检测到丁酸;添加4.4和6.6 mL·kg^-1甲酸组整个青贮过程中无乳酸和挥发性脂肪酸产生,氨态氮/总氮值维持在很低的水平(<12 g·kg^-1TN)。综上所述,添加2.2 mL·kg^-1甲酸的处理在青贮后期酸化作用减弱,使象草的发酵品质和营养品质变差,而添加4.4 mL·kg^-1以上甲酸能够有效地保存象草的营养物质。

关键词: 象草, 甲酸, 青贮, 发酵品质