Schmidt R J, Hu W, Mills J A, Kung L
Department of Animal and Food Sciences, University of Delaware, Newark 19716-2150, USA.
J Dairy Sci. 2009 Oct;92(10):5005-10. doi: 10.3168/jds.2008-1701.
This study was conducted to document the development of populations of lactic acid bacteria (LAB) and Lactobacillus buchneri in alfalfa silage treated with various inoculants. Wilted and chopped alfalfa (45% dry matter) was treated with 1) distilled water (untreated, U), 2) Lactobacillus buchneri 40788 (4 x 10(5) cfu/g; LB), or 3) L. buchneri 40788 (4 x 10(5) cfu/g) and Pediococcus pentosaceus (1 x 10(5) cfu/g; LBPP). Forages were packed into triplicate vacuum-sealed, nylon-polyethylene bags per treatment, and ensiled for 2, 5, 45, 90, and 180 d. Viable (cfu) LAB in forage and silage were quantified by traditional plating on selective agar, and numbers of L. buchneri (cfu-equivalent, cfu-E) were quantified by real-time quantitative PCR. Fresh, untreated forage had 5.52 log cfu of LAB/g and 3.79 log cfu-E of L. buchneri/g. After 2 d of ensiling, numbers of LAB increased to >8 log cfu/g in all silages. In contrast, numbers of L. buchneri in U remained below 4 log cfu-E/g but reached approximately 7 log cfu-E/g in LB and LBPP. From d 5 onward, numbers of L. buchneri in U remained below 6 log cfu-E/g but approached 9 log cfu-E/g in LB and LBPP. The pH was lower in LBPP compared with U and LB after 2 and 5 d of ensiling, but pH was lower for U compared with LB and LBPP thereafter. Treatments LB and LBPP had more acetic acid than U at 45 d of ensiling, which coincided with detectable amounts of 1,2 propanediol. Inoculation with LBPP resulted in silage with the highest concentration of 1,2 propanediol after 180 d of ensiling. From d 45 onward, LB and LBPP silages had lower concentrations of residual water-soluble carbohydrates but had higher concentrations of ammonia-N than U. In conclusion, epiphytic L. buchneri can be detected in alfalfa but this population is unable to lead the silage fermentation. In contrast, when L. buchneri was added to silage as an inoculant, the numbers of L. buchneri (cfu-E) increased markedly but did not dictate fermentation until 45 d of ensiling. These findings help to explain why the response (in increased acetic acid) from the addition of L. buchneri in silages is not immediate.
本研究旨在记录用不同接种剂处理的苜蓿青贮饲料中乳酸菌（LAB）和布氏乳杆菌的菌群发展情况。将萎蔫并切碎的苜蓿（干物质含量45%）用以下物质处理：1）蒸馏水（未处理，U）；2）布氏乳杆菌40788（4×10⁵ cfu/g；LB）；或3）布氏乳杆菌40788（4×10⁵ cfu/g）和戊糖片球菌（1×10⁵ cfu/g；LBPP）。每种处理的草料被装入一式三份的真空密封尼龙 - 聚乙烯袋中，青贮2、5、45、90和180天。通过在选择性琼脂上传统平板计数法对草料和青贮饲料中的活菌（cfu）LAB进行定量，通过实时定量PCR对布氏乳杆菌的数量（cfu当量，cfu - E）进行定量。新鲜的未处理草料中LAB含量为5.52 log cfu/g，布氏乳杆菌含量为3.79 log cfu - E/g。青贮2天后，所有青贮饲料中LAB数量增加至>8 log cfu/g。相比之下，未处理组（U）中布氏乳杆菌数量保持在4 log cfu - E/g以下，但在LB组和LBPP组中达到约7 log cfu - E/g。从第5天起，U组中布氏乳杆菌数量保持在6 log cfu - E/g以下，但LB组和LBPP组接近9 log cfu - E/g。青贮2天和5天后，LBPP组的pH值低于U组和LB组，但此后U组的pH值低于LB组和LBPP组。青贮45天时，LB组和LBPP组的乙酸含量比U组多，同时可检测到1,2 - 丙二醇。青贮180天后，接种LBPP的青贮饲料中1,2 - 丙二醇浓度最高。从第45天起，LB组和LBPP组青贮饲料中残留水溶性碳水化合物浓度较低，但氨态氮浓度高于U组。总之，苜蓿中可检测到附生的布氏乳杆菌，但该菌群无法主导青贮发酵。相比之下，当将布氏乳杆菌作为接种剂添加到青贮饲料中时，布氏乳杆菌数量（cfu - E）显著增加，但直到青贮45天时才主导发酵。这些发现有助于解释为什么在青贮饲料中添加布氏乳杆菌后（乙酸增加）的反应不是立即出现的。
