Institute of Ensiling and Processing of Grass, College of Agro-grassland Science, Nanjing Agricultural Universitygrid.27871.3b, Nanjing, China.
mSphere. 2022 Aug 31;7(4):e0016822. doi: 10.1128/msphere.00168-22. Epub 2022 Jul 18.
To characterize the effects of time of day for harvest on the fermentation parameters, bacterial community, and metabolic characteristics of sorghum-sudangrass hybrid (SSG) silage, SSG (vegetative stage) harvested at 7:00 (AM), 12:00 (M), and 17:00 (PM) on three sunny days were ensiled for 1, 3, 7, 14, 30, and 60 days. Compared to AM silage, M and PM silages were characterized by delayed fermentation, unnormal lower final pH, and lower acetic acid production. In addition, PM silage contained higher residual water-soluble carbohydrates than other silages. After 60 days of ensiling, AM silage was dominated by , whereas the bacterial communities of M and PM silages were complex and mainly composed of bacteria such as , , , Acinetobacter, and . The harvest time affected a wide range of metabolic pathways including "Metabolism" and "Cellular Processes" and "Organismal Systems" in SSG silage. Particularly, at the late stage of ensiling M silage exhibited highest relative abundances of amino acid metabolisms including "glycine, serine, and threonine metabolism," "phenylalanine metabolism," and lowest relative abundances of "lysine biosynthesis." These results suggest that the time of day for harvest could affect the fermentation parameters, bacterial community, and metabolic characteristics of SSG silage. Better SSG silage characteristics could be achieved through morning harvest. Ensiling is a common way for preserving green forages worldwide. Silage fermentation quality can vary greatly depending on the chemical and microbial characteristics of forage crop being ensiled. It is well documented that forages exhibit considerable variations in chemical composition and epiphytic microbiota during daylight. However, the effects of the time of day for harvest on silage fermentation is less investigated. Our results demonstrate that the time of day for harvest could affect the fermentation parameters, bacterial community, and metabolic characteristics of SSG hybrid silage. Harvesting SSG late in the day delayed fermentation process, lowered acetic acid production and final pH, and increased the residual water-soluble carbohydrates content in silage. Moreover, the delayed harvest time increased the relative abundances of bacteria such as , , Acinetobacter, , and , and amino acid metabolisms at the late stage of SSG ensiling. This study highlights the importance of diurnal changes in forage to fermentation characteristics, providing a strategy to improve silage quality through optimizing the harvest time.
为了研究收获时间对高粱-苏丹草混合青贮发酵参数、细菌群落和代谢特性的影响，在 3 个晴天的 7：00（上午）、12：00（中午）和 17：00（下午）收获处于营养生长期的高粱-苏丹草混合青贮，在 1、3、7、14、30 和 60 d 进行青贮。与上午青贮相比，中午和下午青贮的发酵延迟，最终 pH 值较低且乙酸产量较低。此外，下午青贮的残余水溶性碳水化合物含量高于其他青贮。青贮 60 d 后，上午青贮主要由 主导，而中午和下午青贮的细菌群落较为复杂，主要由 、 、 、不动杆菌和 等细菌组成。收获时间影响高粱-苏丹草混合青贮广泛的代谢途径，包括“代谢”和“细胞过程”和“生物体系统”。特别是在青贮后期，中午青贮表现出较高的氨基酸代谢相对丰度，包括“甘氨酸、丝氨酸和苏氨酸代谢”、“苯丙氨酸代谢”和最低的“赖氨酸生物合成”相对丰度。这些结果表明，收获时间会影响高粱-苏丹草混合青贮的发酵参数、细菌群落和代谢特性。通过清晨收获可以获得更好的高粱-苏丹草混合青贮特性。青贮是全世界保存绿色饲料的常用方法。青贮发酵质量受青贮饲料作物的化学和微生物特性影响很大。有大量文献报道，饲料在白天会发生显著的化学组成和附生微生物变化。然而，收获时间对青贮发酵的影响研究较少。我们的结果表明，收获时间会影响高粱-苏丹草混合青贮的发酵参数、细菌群落和代谢特性。傍晚收获会延迟青贮发酵过程，降低乙酸产量和最终 pH 值，并增加青贮中残余水溶性碳水化合物的含量。此外，延迟收获时间会增加 、 、不动杆菌、 、 和 等细菌和在青贮后期的氨基酸代谢相对丰度。本研究强调了饲料日变化对发酵特性的重要性，为通过优化收获时间提高青贮质量提供了策略。
