Li Haiping, Guan Hao, Jia Zhifeng, Liu Wenhui, Ma Xiang, Liu Yong, Wang Hui, Zhou Qingping
Key Laboratory of Superior Forage Germplasm in the Qinghai-Tibetan Plateau, Qinghai Academy of Animal Science and Veterinary Medicine, Qinghai University, Xining, China.
Sichuan Zoige Alpine Wetland Ecosystem National Observation and Research Station, Southwest Minzu University, Chengdu, China.
Front Microbiol. 2022 Jul 19;13:944945. doi: 10.3389/fmicb.2022.944945. eCollection 2022.
The objective of this study is to determine the effect of freeze-thaw condition on the fermentation characteristics, microbial community, and aerobic stability of oat () silage in the Qinghai-Tibet Plateau. Oat forage was harvested at milk ripening stage, ensiled in vacuum-sealed bags, and then stored at (1) a constant temperature of 20°C, as a control (20 group) or (2) subjected to freeze-thaw condition (alternating 20 and -5°C every 12 h; S group). The quality and microbial community in the silage were measured after 1, 3, 7, 14, and 60 days of ensiling, and the aerobic stability was measured after 60 days of ensiling at room temperature or at the two treatment temperatures. The results showed that the higher the pH, the lower the concentration of lactic acid and the ratio of lactic acid/acetic acid of the samples under freeze-thaw condition, as compared to those stored at 20°C. The dry matter content of 20 groups was significantly higher than S group ( < 0.05). While ash, neutral detergent fiber (NDF), acid detergent fiber (ADF), crude protein (CP), and water-soluble carbohydrates (WSC) had no significant difference between two groups. spp., spp., and spp. were the most prevalent bacterial genera in all groups. The abundance of spp. in the 20 group was the highest on day 3 of ensiling ( < 0.05), and it reached the peak on day 14 in the S group, but the abundance in the S group did not exceed 50% during whole fermentation process. The abundance of Enterobacterales and the count of in the S group was significantly higher than 20 group ( < 0.05). Interestingly, the lactic acid concentration was significant correlated with spp. in 20 group, while correlated with spp. in S group. The aerobic stability of the S group was lower than that of the 20 group ( < 0.05). The present study indicates that the freeze-thaw condition led to insufficient fermentation degree of silage by limiting the fermentation of spp. and severely reduced the aerobic stability of oat silage.
本研究的目的是确定冻融条件对青藏高原燕麦（）青贮饲料发酵特性、微生物群落及有氧稳定性的影响。燕麦牧草在乳熟期收获，装入真空密封袋青贮，然后分别在（1）20°C恒温条件下储存作为对照（20组），或（2）置于冻融条件下（每12小时交替在20°C和 -5°C之间；S组）。青贮1、3、7、14和60天后测定青贮饲料的质量和微生物群落，青贮60天后在室温或两种处理温度下测定有氧稳定性。结果表明，与在20°C储存的样品相比，冻融条件下样品的pH值越高，乳酸浓度和乳酸/乙酸比值越低。20组的干物质含量显著高于S组（<0.05）。而两组之间的灰分、中性洗涤纤维（NDF）、酸性洗涤纤维（ADF）、粗蛋白（CP）和水溶性碳水化合物（WSC）无显著差异。所有组中，芽孢杆菌属、乳酸菌属和肠杆菌属是最普遍的细菌属。20组中芽孢杆菌属的丰度在青贮第3天最高（<0.05），S组在第14天达到峰值，但S组在整个发酵过程中的丰度未超过50%。S组中肠杆菌科的丰度和大肠杆菌的数量显著高于20组（<0.05）。有趣的是，20组中乳酸浓度与芽孢杆菌属显著相关，而S组中与乳酸菌属相关。S组的有氧稳定性低于20组（<0.05）。本研究表明，冻融条件通过限制芽孢杆菌属的发酵导致青贮饲料发酵程度不足，并严重降低了燕麦青贮饲料的有氧稳定性。
