Comparison of fermentation characteristics of Italian ryegrass (Lolium multiflorum Lam.) and guineagrass (Panicum maximum Jacq.) during the early stage of ensiling
Comparison of fermentation characteristics of Italian ryegrass (Lolium multiflorum Lam.) and guineagrass (Panicum maximum Jacq.) during the early stage of ensiling
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DOI：
10.5713/ajas.2005.1727
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发表时间：
2005-12-01
期刊：
影响因子：
--
通讯作者：
Masuda, Y
中科院分区：
文献类型：
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作者：
Shao, T;Zhang, ZX;Masuda, Y
以温带牧草多花黑麦草（Lolium multiflorum Lam.）为试材，研究了其青贮前期的发酵特性及单、双组分组成。和一种热带草，天竺葵（Panicum maximum Jacq.）。将实验室筒仓保持在设定为25 ℃的室内，然后分别在青贮后0.5、1、2、3、5和7天（多花黑麦草为14天）打开。多花黑麦草青贮在青贮的前5天由于乳酸的快速大量产生而导致pH快速大幅度下降，成功实现了乳酸型发酵;青贮结束时（14天）乳酸/乙酸和乳酸含量高，pH值低（3.74）、乙酸、乙醇和氨-N/总氮，没有或仅少量丁酸、戊酸和丙酸。在整个青贮期内，pH值缓慢下降，乳酸含量缓慢上升，最终pH值较高，乳酸、乙酸、总挥发性脂肪酸和总有机酸含量较低。在意大利黑麦草青贮，单和二-双组分大幅下降，在最初的0.5天（12小时）的青贮。蔗糖在青贮的0.5d内迅速消失，而果糖和葡萄糖含量则表现为先上升后下降的变化趋势。在青贮的最初0.5d内，单果糖和双果糖含量下降幅度最大，主要是由于植物呼吸作用的影响，而果糖和葡萄糖含量在青贮的早期没有上升，这是因为温带禾本科牧草中没有果聚糖水解为果糖和葡萄糖。在两种青贮饲料中，在青贮的最初5天内，单-和二-淀粉组分的减少速率按葡萄糖>果糖>蔗糖的顺序排列，这表明葡萄糖和果糖可能比蔗糖更有利地被微生物利用，并且葡萄糖是第一发酵底物。结果表明，高含水量多花黑麦草青贮料发酵品质较好，主要是由于青贮初期乳酸菌占优势，乳酸发酵活跃。这些结果可以解释为快速的植物汁液释放和高活性的植物酶水解果聚糖转化为果糖和葡萄糖，这刺激了同型发酵乳酸菌的生长。在青贮中，温带草的物理特性可以确保发酵阶段的快速开始，这是由于在青贮的初始阶段期间水溶性碳水化合物的损失较小，并且为乳酸菌提供了足够的水溶性碳水化合物。以干物质含量中等、单双组分初始含量高的稗草为原料制成的青贮饲料是稳定的青贮饲料。这可以解释为在青贮的非常早期阶段，由于粗糙的孔隙度和茎结构的热带草的性质，细胞分解和汁液释放的限制，空气的较高的掺入。这些物理特性通过延长呼吸作用和好氧微生物活动的阶段延迟了乳酸菌发酵阶段的开始，导致水溶性碳水化合物损失较高，乳酸菌发酵底物短缺。
The fermentation characteristics and mono- and di-saccharides compositions during the early stage of ensiling were studied with a temperate grass, Italian ryegrass (Lolium multiflorum Lam.) and a tropical grass, guineagrass (Panicum maximum Jacq.). The laboratory silos were kept in the room set at 25 degrees C, and then were opened on 0.5, 1, 2, 3, 5 and 7 days (14 days in Italian ryegrass) after ensiling, respectively. The Italian ryegrass silage showed a fast and large pH decrease caused by a fast and large production of lactic acid during the first 5 days of ensiling and succeeded to achieve lactic acid type fermentation; high lactic acid/acetic acid and lactic acid content at the end of ensiling (14 days), low values of pH (3.74), acetic acid, ethanol and ammonia-N/total nitrogen, none or only small amounts of Butyric acid, valeric acid and propionic acid. The guineagrass silage showed a slow decrease in pH and a slow increase in lactic acid content during the full ensiling period, causing a high final pH value, low contents of lactic acid, acetic acid, total volatile fatty acids and total organic acids. In Italian ryegrass silage, mono- and di-saccharides compositions decreased largely within the initial 0.5 day (12 h) of ensiling. Sucrose disappeared rapidly within the initial 0.5 day of ensiling, but fructose and glucose contents showed an initial rise by the activity of enzymes in plant tissues, and then decreased gradually. On the other hand, the contents of mono- and di-saccharides in guineagrass showed the largest decreases due mainly to plant respiration within the initial 0.5 day of ensiling, and no initial rises in fructose and glucose contents during the early stage of ensiling because of the absence of fructans which are hydrolyzed into fructose and glucose in temperate grasses. In both silages, the rate of reduction in mono- and di-saccharides compositions within the initial 5 days of ensiling was ranked in the order of glucose>fructose>sucrose, suggesting that glucose and fructose might be more favorably utilized than sucrose by microorganisms and glucose is the first fermentation substrate. It was concluded that the silage made from Italian ryegrass with high moisture content had a good fermentation quality owing to the dominance of lactic acid bacteria and active lactic acid fermentation during the initial stage of ensiling. These results can be explained by rapid plant sap liberation and the high activity of plant enzyme hydrolyzed fructans into fructose and glucose within the initial 2 days of ensiling, which stimulate the homofermentative lactic acid bacteria growth. In ensiling a temperate grass, the physical characteristics may ensure the rapid onset of fermentation phase, which results from the smaller losses of water-soluble carbohydrates during the initial stage of ensiling and providing sufficient water-soluble carbohydrates for lactic acid bacteria. The silage made from guineagrass with intermediate dry matter and high initial mono- and di-saccharides content was stable silage. This could be explained by the higher incorporation of air during the very early stage of ensiling and the restriction of cell breakdown and juice release due to the,properties of a tropical grass with coarse porosity and stemmy structures. These physical characteristics delayed the onset of lactic acid bacteria fermentation phase by extending the phases of respiration and aerobic microorganisms activity, causing the higher loss of water-soluble carbohydrates and the shortage of lactic acid bacteria fermentation substrates.