Microbial Community and Fermentation Quality of Alfalfa Silage Stored in Farm Bunker Silos in Inner Mongolia, China

Abstract

Alfalfa is conserved in silo-type bunkers in the cold and humid regions of Inner Mongolia, China. Its quality is essential to ensure a healthy and sustainable dairy production. However, the impact of environmental factors on the microbiota and fermentation products of alfalfa silage remains unclear. The present research examined changes in the microbiota and fermentation products and their association with environmental parameters in 72 samples collected from 12 farms located at 4 different latitudes and longitudes across four regions. The samples were labeled with distinct codes, A, B, and C, from the cold–rainy region, D, E, and F, from the warm–rainy region, G, H, and I from the cold–dry region, and J, K, and L from the warm–dry region. The lactic acid levels ranged from 14.25 to 24.27 g/kg of DM across all samples. The pH and concentrations of NH3-N and butyric acid in samples A, B, and H were higher (p < 0.01) than in the other samples. Samples D and E had higher acetic acid concentrations and 1, 2-propanediol content (p < 0.01). The fresh material was dominated by Pantoea and Pseudomonas, whereas Lactobacillus was the most dominant genus in all silages, except for the B silage. The A, B, and H silages contained more Clostridium but less Lactobacillus than the other silages. The lactic acid levels were strongly associated with Lactobacillus plantarum, Weissella paramesenteroides, Lactobacillus acetotolerans, Pedobacter borvungensis, and Lactobacillus brevis (p < 0.01). In contrast, the pH and the NH3-N and butyric acid concentrations were strongly associated (p < 0.01) with the presence of Clostridium estertheticum. A correlation analysis revealed that precipitation, temperature, longitude, and latitude were the most critical factors influencing epiphytic microbes in the fresh material. After silage fermentation, low-temperature conditions significantly affected the fermentation products and microbial community composition. In conclusion, the microbial community of silages is distinctive in cold and humid regions, and climatic parameters ultimately affect the microbiota and fermentation products. Furthermore, the findings of this study demonstrate that Illumina MiSeq sequencing combined with environmental factor assessment might provide new information about the microbiota composition and fermentation quality of silages, facilitating the achievement of high-quality silage.