乳酸链球菌素对瘤胃体外发酵、甲烷生成及功能菌群数量的影响

Effects of nisin on in vitro fermentation, methanogenesis and functional microbial populations of the rumen

摘要:

[目的] 旨在通过体外静态模拟瘤胃发酵法研究乳酸链球菌素（NI）对瘤胃发酵、甲烷生成及功能菌群数量的影响。[方法] 以不添加任何添加剂处理做阴性对照（NC），以莫能菌素（MON,5 μmol/L）做阳性对照，试验组NI添加水平分别为3（NI-3）、9（NI-9）和27 mg/100 mL（NI-27），每个处理4个重复，分别于培养后的0、3、6、9、12、24 h测定产气量和甲烷产量。培养24 h后，采集发酵液样品，用于发酵参数和菌群数量的测定。[结果] 与NC组相比，添加NI和MON均能显著降低产气量和甲烷产量（P<0.05）；添加NI对pH值、干物质消失率（DMD）和有机物消失率（OMD）无显著影响（P0.05）；NI-9处理组与NC组相比氨态氮浓度显著降低（P<0.05），而NI-3和NI-27组氨氮浓度没有显著变化（P0.05）；相比而言，MON处理组DMD、OMD和氨氮浓度与NC组相比均显著降低（P<0.05），而pH值与其他各处理组相比没有差异（P0.05）；与NC组相比，NI各处理组和MON组乙酸浓度及乙丙比均显著降低（P<0.05），丙酸浓度显著提高（P<0.05）。功能菌方面，qPCR结果显示添加NI和MON对总菌和拟杆菌门数量均无显著影响（P0.05）；与NC相比，添加NI对原虫、甲烷菌、真菌和厚壁菌门数量均无显著影响（P0.05），而MON组原虫、甲烷菌、真菌和厚壁菌门数量显著降低（P<0.05）；NI和MON处理均显著提高了硫还原菌和C.aminophilum数量（P<0.05），但C.sticklandii数量不受影响（P0.05）。[结论] 添加适宜浓度的NI可降低瘤胃甲烷与氨的生成，但并不影响饲料消化，这种发酵模式的改变可能与瘤胃功能菌群数量与多样性的变化密切相关。

Abstract:

[Objective] This study was conducted to evaluate the effects of nisin on in vitro fermentation, methanogenesis and functional microbial populations of the rumen.[Methods] The negative control did not contain any additives. Monensin (5 μmol/L) was added as positive control. Nisin was added at 3 doses:3 (NI-3), 9 (NI-9), and 27 mg/100 mL (NI-27). Each treatment contained 4 replicates. Gas and methane production was measured at 0, 3, 6, 9, 12, and 24 h after incubation. Samples of culture were collected at 24 h, and used to measure rumen fermentation parameters and functional microbial populations.[Results] Compared with negative control, both nisin and monensin addition dramatically reduced gas and methane production (P<0.05). Nisin addition had no effect on pH, dry matter degradability, and organic matter degradability (P0.05). Ammonia concentration was reduced by NI-9 (P<0.05), but was not influenced by NI-3 and NI-27 (P0.05). In contrast, monensin addition significantly lowered dry matter degradability, organic matter degradability, and ammonia concentration (P<0.05), but had no influence on pH (P0.05). Compared with negative control, both nisin and monensin addition significantly reduced acetate concentration and acetate-propionate ratio (P<0.05), and increased propionate concentration (P<0.05). Quantitative real-time PCR results showed that both nisin and monensin addition had no effects on the populations of total bacteria and Bacteroides (P0.05). Compared with negative control, the populations of protozoa, methanogens, fungi and Firmicutes were not influenced by nisin (P0.05), but were significantly reduced by monensin addition (P<0.05). Both nisin and monensin addition significantly increased the populations of sulfur-reducing bacteria and Clostridium aminophilum (P<0.05), but had no influence on the population of Clostridium sticklandii (P0.05).[Conclusion] Appropriate nisin addition could reduce methanogenesis and ammoniagenesis, while had no adverse effect on feed digestion. These effects are probably associated with the variation of rumen functional microbial populations and communities.