Insights into the microbiome and metabolome assembly during short-term storage of native grass hay

Microbial diversity is a key determinant of quality deterioration in native grasses. However, it is still poorly understood how microbial community succession affects metabolite profiles during storage. The objectives of this study were to determine patterns of nutrient changes, track the succession of fungal communities, and observe changes in metabolites during storage of native grasses. To carry out this study, nutrient changes in native grass samples were compared in fresh samples as well as after 0, 5, 10, 15, and 30 days of storage, and the microbial community was determined using internal transcribed spacer (ITS) sequencing technology. Metabolite changes in native grass hay after 0 and 30 days of storage were examined by untargeted metabolomics techniques. The results showed that crude protein and water-soluble carbohydrate of native grass hay showed a decreasing trend with storage time. Based on phylum level, the Ascomycota showed significant differences (P < 0.05) in native grass harvesting, processing and storage, and Kabatiella and Cryptococcus differed significantly (P < 0.05) at the genus level. A total of 322 metabolites were identified in the metabolites of native grass hay. Our findings suggested that Kabatiella was associated with the production of flavonoids such as Cyanidin 3-(2g-glucosylrutinoside) and diosmetin-7-o-rutinoside. KEGG enrichment analysis showed that the important enrichment pathways of different metabolites were mainly related to tryptophan metabolism and unsaturated fatty acid biosynthesis. This study provides a comprehensive understanding of the changes in nutrient quality, fungal community succession and metabolites of native grass hay during storage, which provides a theoretical basis for the safe storage of native forage.