The aim of this study was to reveal the reconstitution dynamics of alfalfa microbiota and their contribution to the fermentation quality of Napier grass silages. Napier grass was harvested at approximately 20% dry matter content, chopped to a theoretical length of cut of 2 to 3 cm, and ensiled in laboratory polyethylene plastic bags (400 × 250 mm) for 30 d. The Napier grass was treated with the following: natural fermentation and distilled water (NG), inoculum of alfalfa microbiota (AM), gamma-ray irradiation and distilled water (IR), and gamma-ray radiation and alfalfa microbiota (IR+AM). Three milliliters of inoculum (containing 8.93 log cfu/mL lactic acid bacteria, 9.76 log cfu/mL Enterobacteriaceae, 5.94 log cfu/mL yeast, and 6.53 log cfu/mL mold) eluted from equivalent fresh alfalfa (450 g) was added to each silo of AM and IR+AM treatments, and 3 mL of distilled water was added to the silo of the NG and IR treatments. Three triplicate silos per treatment were opened on d 1, 3, 5, 7, 14, and 30 for sampling and analysis of fermentation quality and bacterial community. Relative to the NG silages, IR+AM silages exhibited a higher lactic acid concentration. The higher acetic acid concentration in NG than in IR+AM silages after 7 d of ensiling was attributed to the dominant genus of Leuconostoc (64.29-49.04%). Adding alfalfa microbiota to sterile Napier grass could increase ammonia-N concentration compared with NG and IR silages after 3 d of ensiling. Leuconostoc was the most predominant genus in NG silages, followed by Lactobacillus. Pediococcus had a greater relative abundance than the indigenous microorganisms and was exclusively found in AM and IR+AM silages, whereas Lactobacillus exhibited a slight increase after 30 d of ensiling (relative abundance in each silage: 6.29 vs. 3.82%, respectively). Lactobacillus was the predominant genus in IR silages since the onset of the ensiling. These results suggest that alfalfa microbiota affected bacterial community succession in Napier grass silages, which in turn affected the fermentation products. Adding alfalfa microbiota to sterile Napier grass could decrease acetic acid concentration compared with NG silages; however, it increased ammonia-N concentration compared with IR silages after 3 d of ensiling.

中文翻译：

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苜蓿菌群对新鲜或无菌纳皮草青贮饲料发酵质量和细菌群落演替的影响。

这项研究的目的是揭示苜蓿微生物群的重建动态及其对纳皮尔青贮青贮饲料发酵质量的影响。收获的纳皮草的干物质含量约为20％，切成理论的2到3厘米的切段长度，并在实验室聚乙烯塑料袋（400×250毫米）中青贮30 d。纳皮尔草经过以下处理：自然发酵和蒸馏水（NG），苜蓿菌群接种物（AM），γ射线辐照和蒸馏水（IR）以及γ射线辐射和苜蓿菌群（IR + AM） 。将每毫升新鲜紫花苜蓿（450 g）洗脱的三毫升接种物（包含8.93 log cfu / mL乳酸菌，9.76 log cfu / mL肠杆菌科，5.94 log cfu / mL酵母和6.53 log cfu / mL霉菌洗脱） AM和IR + AM处理的筒仓，将3 mL蒸馏水添加到NG和IR处理的料仓中。在第1、3、5、7、14和30天，每个处理打开三个重复的筒仓，以采样和分析发酵质量和细菌群落。相对于NG青贮，IR + AM青贮具有较高的乳酸浓度。灌浆7 d后，NG中的乙酸浓度高于IR + AM青贮物中的乙酸浓度，归因于Leuconostoc的优势菌属（64.29-49.04％）。与青贮和红外青贮相比，在无菌的纳皮尔草中添加苜蓿菌群可以增加氨氮的浓度。Leuconostoc是NG青贮饲料中最主要的属，其次是乳杆菌。肺炎球菌的相对丰度比本地微生物更大，并且仅存在于AM和IR + AM青贮饲料中，乳酸菌在青贮30 d后略有增加（每种青贮饲料的相对丰度分别为6.29和3.82％）。自青贮以来，乳杆菌是IR青贮饲料中的主要属。这些结果表明，苜蓿微生物群影响了纳皮尔草青贮饲料中细菌群落的演替，进而影响了发酵产物。与NG青贮饲料相比，在无菌的Napier草中添加苜蓿菌群可以降低乙酸浓度。然而，青贮3 d后，与IR青贮相比，氨氮浓度增加。这些结果表明，苜蓿微生物群影响了纳皮尔草青贮饲料中细菌群落的演替，进而影响了发酵产物。与NG青贮饲料相比，在无菌的Napier草中添加苜蓿菌群可以降低乙酸浓度。然而，青贮3 d后，与IR青贮相比，氨氮浓度增加。这些结果表明，苜蓿微生物群影响了纳皮尔草青贮饲料中细菌群落的演替，进而影响了发酵产物。与NG青贮饲料相比，在无菌的Napier草中添加苜蓿菌群可以降低乙酸浓度。然而，青贮3 d后，与IR青贮相比，氨氮浓度增加。