冻融对燕麦青贮有氧暴露阶段细菌和真菌演替的影响

Effects of freeze-thaw on bacterial and fungal succession during aerobic exposure stage of oat silage

摘要:

目的 为探索冻融条件对燕麦青贮在有氧暴露阶段的影响。方法 将燕麦在冻融条件(20 ℃和-5 ℃每12 h交替1次，S组)下青贮60 d后进行有氧暴露监测，并以恒温20 ℃ (20组)作为对照。分别在青贮60 d和有氧暴露1、3、5 d取样进行发酵品质和营养品质的测定，同时进行16S rRNA基因和ITS测序。结果 随着有氧暴露时间的延长pH值升高。与原冻融温度下的有氧暴露相比，室温下的有氧暴露导致pH值和氨态氮含量上升更快，乳酸和乙酸含量下降也更快。S组，特别是室温下的有氧暴露条件下，丙酸和丁酸的生成速度更快。随着有氧暴露的推进，肠杆菌和酵母菌数量不断增加，而乳酸菌数量不断减少(P<0.05)。细菌的Shannon指数和Simpson指数随着有氧暴露时间的延长而增加，乳酸菌的丰度不断降低。有氧暴露第3天时，细菌群落结构出现明显差异。与原温度下的有氧暴露相比，室温下的有氧暴露加速了微生物的更替。S组中指征腐败的酵母菌和霉菌的种类及数量更多。结论 冻融条件加速了燕麦青贮在有氧暴露阶段的变败过程，尤其是在室温下进行有氧暴露时。本研究为高寒区燕麦青贮的高品质调制及存放提供理论指导。

关键词:青贮;冻融;有氧稳定性;燕麦

Abstract:

Objective To explore the effects of freeze-thaw on oat silage during the aerobic exposure stage.Methods Oat silage was stored at a constant temperature (20 ℃, group 20, control) and freeze-thaw conditions (20 ℃ and -5 ℃ alternating every 12 h, group S) for 60 days and then subjected to aerobic exposure. Samples were collected on day 60 of ensiling and after aerobic exposure for 1, 3, and 5 days, respectively, for the determination of fermentation quality and nutritional quality as well as for 16S rRNA gene and ITS sequencing.Results The pH rose as the aerobic exposure was prolonged. The samples subjected to aerobic exposure at room temperature showed more rapid increases in ammonia nitrogen content and pH and more rapid decreases in lactic acid and acetic acid content than those subjected to aerobic exposure at freeze-thaw temperatures. Propionic acid and butyric acid were produced more rapidly in the S group, especially in the case of aerobic exposure at room temperature. Enterobacteria and yeast increased while lactic acid bacteria decreased as the aerobic exposure was prolonged (P<0.05). Shannon and Simpson indices of bacteria increased during aerobic exposure, and the relative abundance of lactic acid bacteria kept decreasing. The bacterial community structure presented a significant difference on days 3 of aerobic exposure, and microbial succession was accelerated by aerobic exposure at room temperature compared with that at the freeze-thaw temperature, with more species and higher counts of yeast and molds indicative of spoilage in the S group.Conclusion Freeze-thaw accelerated aerobic deterioration, especially aerobic exposure at room temperature. This study provides theoretical guidance for high-quality modulation and storage of oat silage in alpine areas.

Key words:silage;freeze-thaw;aerobic stability;oat