Changes in silage quality, bacterial community dynamics, and metabolic profiles in whole-crop maize silage

This study aimed to investigate the silage quality, bacterial community, and predicted functional profiles during the ensiling of whole-crop maize (Zea mays L.). Maize was harvested at dough stage and ensiled in laboratory-scale silos (1-L capacity). Triplicate silos were sampled after 1, 3, 7, 15, 30, and 60 d of ensiling. The bacterial communities on Day 3 and Day 60 were assessed through high throughput sequencing technology, and 16S rRNA gene-predicted functional profiles were analyzed according to the KEGG using Tax4Fun. After 60 d of ensiling, the maize silages had large amounts of lactic acid (similar to 69.0 g dry matter [DM] kg(-1)), and low pH (similar to 3.64), butyric acid (similar to 1.31 g DM kg(-1)), and ammonia N (similar to 64.9 g total N kg(-1)). Lactobacillus was the most dominant genus during the early and late stages of fermentation. After ensiling, the metabolism of amino acid, energy, cofactors and vitamins was inhibited by 17.5, 16.3, and 16.0% respectively, whereas the metabolism of nucleotide and carbohydrate was enhanced by 37.1 and 10.3%, respectively. The promotion of 1-phosphofructokinase and pyruvate kinase (65.9 and 32.5%, respectively) may stimulate the lactic acid fermentation, and the enhancement of arginine deiminase (61.8%) could help lactic acid bacteria to tolerate the acid environment. Overall, the high throughput sequencing technology, combined with 16S rRNA gene-predicted functional analyses, revealed differences in maize silage related to shifts in the bacterial community consistent with increased abundance of inferred enzymatic pathways. This approach could provide comprehensive insights into bacterial community and functional profiles to further improve the silage quality.

Automated summary

This study investigated the silage quality, bacterial community, and predicted functional profiles during the ensiling of whole-crop maize. The results showed that after 60 days of ensiling, the maize silages had high levels of lactic acid, low pH, butyric acid, and ammonia N. Lactobacillus was the dominant genus during fermentation. The metabolism of amino acid, energy, cofactors and vitamins was inhibited, while the metabolism of nucleotide and carbohydrate was enhanced. Overall, this approach provided comprehensive insights into bacterial community and functional profiles to improve silage quality.