Effects of different harvest frequencies on microbial community and metabolomic properties of annual ryegrass silage

Abstract

In this study, we analyzed the fermentation quality, microbial community, and metabolome characteristics of ryegrass silage from different harvests (first harvest-AK, second harvest-BK, and third harvest-CK) and analyzed the correlation between fermentative bacteria and metabolites. The bacterial community and metabolomic characteristics were analyzed by single-molecule real-time (SMRT) sequencing and ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS/MS), respectively. After 60 days of ensiling, the pH of BK was significantly lower than those of AK and CK, and its lactic acid content was significantly higher than those of AK and CK. Lactiplantibacillus and Enterococcus genera dominate the microbiota of silage obtained from ryegrass harvested at three different harvests. In addition, the BK group had the highest abundance of Lactiplantibacillus plantarum (58.66%), and the CK group had the highest abundance of Enterococcus faecalis (42.88%). The most annotated metabolites among the differential metabolites of different harvests were peptides, and eight amino acids were dominant in the composition of the identified peptides. In the ryegrass silage, arginine, alanine, aspartate, and glutamate biosynthesis had the highest enrichment ratio in the metabolic pathway of KEGG pathway enrichment analysis. Valyl-isoleucine and glutamylvaline were positively correlated with Lactiplantibacillus plantarum. D-Pipecolic acid and L-glutamic acid were positively correlated with Levilactobacillus brevis. L-phenylalanyl-L-proline, 3,4,5-trihydroxy-6-(2-methoxybenzoyloxy) oxane-2-carboxylic acid, and shikimic acid were negatively correlated with Levilactobacillus brevis. In conclusion, this study explains the effects of different harvest frequencies on the fermentation quality, microbial community, and metabolites of ryegrass, and improves our understanding of the ensiling mechanisms associated with different ryegrass harvesting frequencies.

Preservation characteristics and bacterial communities of crimped ensiled barley grains modulated by moisture content and additive application

“…The combined evaluation of both axes in the ordination plot discriminated samples produced under low MC separated from the other MC levels, but together with the raw material before ensiling. In other studies using grass silages ( Franco et al, 2022 ; Fu et al, 2022 ), the raw material was identified separately from the samples after fermentation, forming a cluster of its own, which differs from our result, since here the raw material was grouped together with low MC silages. This indicates that the bacterial community structures of raw material and low MC silages were very similar, with a minor difference for LAB treated silages at low MC, which clustered a little apart, but still close to the raw material and other low MC silages.…”

“…The alpha diversity estimates of the raw material and the ensiled samples are presented in Table 3 . The grain raw material showed greater alpha diversity than most of the ensiled samples for all indexes evaluated, which is in line with Fu et al (2022) , who investigated bacterial ecology in ryegrass raw material and silages. Additionally, there was a decreasing linear effect in alpha diversity with increasing barley grain MC in all additive treatments except CONT.…”

Fermentation quality and bacterial ecology of red clover dominated silage modulated by different management factors

“…Silages showed lower diversity of bacterial communities than the raw material for all indexes evaluated. This is in line with Fu et al (2022), who investigating ryegrass silages found greater bacterial diversity in the raw material. There was no significant effect of compaction and contamination on alpha diversity, but some differences were observed between the additive treatments.…”

“…In general terms, anaerobic fermentation is a metabolic process that starts with the activity of undesirable microorganisms from the raw materials, but these are suppressed and gradually replaced by lactic acid bacteria, which mostly dominate the fermentation process (Ni et al, 2017). Consequently, the raw material remained apart and distant from the clusters of silages, which was the same pattern found by Fu et al (2022). This can potentially be explained by the inability of some epiphytic microorganisms on the foliar surface of the plant to survive under the anaerobic and acidic silage environments.…”

“…Although Firmicutes was a phylum of small contribution from epiphytic communities in the raw material, they dominated the fermentation in most silages. Proteobacteria have been observed to be the most abundant phylum in various silage raw materials such as ryegrass (Fu et al, 2022), maize (Keshri et al, 2018) and timothy (Franco et al, 2022), and although it decreased in proportion in the silages, it still tended to occupy the second position of most abundant phyla in the silages. Shifts of Proteobacteria and Firmicutes from raw material to silages was the same as observed by Keshri et al (2018) when studying maize silages and Franco et al (2022) studying timothy grass silages.…”