摘要
【目的】合理利用牧草资源,为新疆南疆地区畜牧业提供优质青贮,研究探讨了花果期盐穗木青贮后的营养价值和发酵品质,同时为提高青贮饲料发酵品质筛选提供乳酸菌资源。【方法】以新疆阿克苏地区花果期盐穗木为原料制作实验室小剂量自然发酵青贮,在发酵第150天时对比青贮前后盐穗木的干物质(DM)、粗蛋白(CP)、可溶性糖(WSC)、中性洗涤纤维(NDF)和酸性洗涤纤维(ADF)的含量变化,测定盐穗木青贮的p H、氨态氮(NH3-N)、乳酸(LA)、乙酸(AA)、丙酸(PA)和丁酸(BA)含量,并采用实验室纯培养方法结合生理生化分析,对青贮中乳酸菌的种类和形态学进行分类,通过葡萄糖发酵产酸产气试验、细菌微量生化反应碳源发酵试验、耐盐试验、耐酸试验和温度生长试验等生理生化试验对所筛选菌株进行研究。运用核酸Blast技术,将所测序列与Gen Bank数据库进行对比,选择并下载与所测序列同源性最高的已知分类地位的菌种,与本试验所测菌株的序列一起,采用Clustal进行比对,用MEGA5.0绘制系统发育树,确定各菌株分类地位,对分离的菌株进行种属鉴定。【结果】与青贮前相比,由于乳酸菌发酵利用原料中的糖类物质导致青贮后盐穗木中的干物质和可溶性糖含量下降,同时在青贮发酵过程中盐穗木茎秆中难降解的水溶性碳水化合物被乳酸菌降解为易被利用的纤维,导致中性洗涤纤维和酸性洗涤纤维的含量升高,青贮p H为4.250—4.286,乳酸含量为60.923—61.283属于优良品质青贮饲料的范围。从自然发酵盐穗木青贮中分离得到3株粪肠球菌(Enterococcus faecium)、1株屎肠球菌(Enterococcus lactis)、2株蜡状芽孢杆菌(Bacillus cereus)、1株戊糖乳杆菌(Lactobacillus pentosus)、1株植物乳杆菌(Lactobacillus plantarum)和1株布氏乳杆菌(Lactobacillus buchneri)。9株菌均能在p H4—7环境下能生长,在3.0%和6.5%Na Cl条件下及10—45℃范围内生长,且生长状况良好,同时能利用D-葡萄糖、D-甘露糖、纤维二糖、D-甘露醇、D-果糖、蔗糖等多种碳源。其中,戊糖乳杆菌(Lactobacillus pentosus)、布氏乳杆菌(Lactobacillus buchneri)和植物乳杆菌(Lactobacillus plantarum)产酸速率和生长速率较快,且具有很强的耐酸耐盐能力,在5—45℃范围内生长良好。【结论】将盐穗木制成青贮后其营养成分含量和发酵品质均处于良好水平,可将戊糖乳杆菌(Lactobacillus pentosus)、布氏乳杆菌(Lactobacillus buchneri)和植物乳杆菌(Lactobacillus plantarum)这3株菌选作青贮饲料制作过程中的添加剂。
【Objective】In order to make rational use of forage resources to provide high quality silage for animal husbandry in southern Xinjiang, the nutritional value and fermentation quality of Halostachys caspica silage after flowering and fruiting stage were discussed in this study, and the Lactobacillus resources were provided for screening silage fermentation quality. 【Method】A small dose natural fermented silage was made in the laboratory of flower and fruit period in the Akesu area of Xinjiang province. After 150 d fermentation, the contents of dry matter, crude protein, soluble sugar, neutral detergent fiber and acid washing fiber were compared before and after silage, and the contents of p H, ammonia nitrogen, lactic acid, acetic acid, propionic acid and butyric acid in silage were measured. Combining with the physiological and biochemical analysis, the pure culture method from silage microbial analysis was adopted to investigate the species, morphological, and physiological-biochemical characteristics of lactic acid bacteria from Halostachys caspica silage in Xinjiang. The DNA Blast technique was used to compare the measured sequence with the Gen Bank database, thus the species of the known classified status of the highest homology of the tested sequence were selected and downloaded. Together with the sequence of the strains tested in this test, the strains were compared with the Clustal, and the phylogenetic tree was plotted with MEGA5.0 to determine the classification status of the strains and to separate the isolates. As a result, the strains were identified. 【Result】Compared with pre silage, dry matter and soluble sugar content in raw materials decreased after lactic acid bacteria fermentation. At the same time, in the process of silage fermentation, the water-soluble carbohydrates, which were difficult to degrade in the stem, were degraded by lactic acid bacteria to the fibers those were easily used by domestic animals, which led to the increase of the content of neutral detergent fiber and acid washing fiber. Silage p H was 4.254—4.286, and lactic acid content was 60.923—61.283 mg·m L-1, which belonged to the range of good quality silage. 9 strains of lactic acid bacteria were isolated and were mainly Enterococcus faecium, Enterococcus lactis, Bacillus cereus, Lactobacillus pentosus, Lactobacillus plantarum, Lactobacillus buchneri. 9 strains of lactic acid bacteria were found in the range of p H 4—7, and grew well under the condition of 3% and 6.5% concentration of Na Cl, at the same time, the bacteria also grew well between 10 °C and 45 °C. It could also use D-glucose, D-mannose, cellobiose, D-mannitol, D-fructose, sucrose and many other carbon sources. Among them, Lactobacillus pentosus and Lactobacillus buchneri had higher acid production rate and faster growth rate, which showed strong acid and salt tolerance, thrived in the 5—45 °C range, and could be applied to the preparation of silage additives. 【Conclusion】The nutrient content and fermentation quality of the Halostachys caspica were in good level after green storage. The 3 strains of Lactobacillus pentosus, Lactobacillus buchneri, and Lactobacillus plantarum could be selected as additives in the process of making silage.
引文
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