Packing density has a significant influence on the outcome of ensiling forage. In this study, we aim to investigate the effect of packing density on the ensiling properties, microbiome, and in vitro digestibility of barley silages. Barley was ensiled in polyethylene drum silos (30 L) with respective densities of 600, 650, 700, and 750 kg/m3 fresh matter (FM), and stored for 60 days. The bacterial communities, fermentation quality, and in vitro digestibility were analyzed. Fresh barley had a low count of lactic acid bacteria (LAB, 104 cfu/g of FM), and Lactobacillus was nearly undetectable (<1%). Increasing the packing density decreased the pH and the content of ammonia nitrogen (NH3-N), ethanol, neutral detergent fiber (NDF), and acid detergent fiber (ADF) of barley silage (p < 0.05), and increased in vitro digestibility of dry matter, NDF, ADF, and DM recovery (p < 0.05). A higher packing density decreased the abundances of Enterobacter (from 47.4% to 35.4%) and Clostridium (from 13.5% to 3.8%), and increased the abundance of Lactobacillus (from 1.8% to 17.0%). Thus, packing density positively correlated with Lactobacillus (p < 0.05) but negatively correlated with Enterobacter (p < 0.05). The pH and the content of ethanol were positively correlated with Enterobacter (p < 0.05) but negatively correlated with Lactobacillus (p < 0.05). In conclusion, the density of 750 kg/m3 FM resulted in the highest silage quality of the densities tested.

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Oat natural silage is rich in Enterobacteriaceae , increasing gas production and fermentation loss. Lactic acid bacteria interact synergistically to form a dominant community during ensiling. Pediococci grow vigorously in the early stage of fermentation and create an anaerobic environment. Lactobacilli inhibit the harmful microorganisms and result in cleaner fermentation of oat silage.

This study aimed to investigate the effects of lactic acid bacteria (LAB) inoculants on the fermentation quality, microbial compositions, and predicted functional profiles of forage oat. The forage oat was inoculated with distilled water, Lentilactobacillus buchneri (LB), and Lactiplantibacillus plantarum (LP) as the control (CON), LB and LP treatments, respectively, and the addition of Lentilactobacillus buchneri (LB) or Lactiplantibacillus plantarum (LP) resulted in 1 × 106 colony-forming units/g of fresh weight. After 30 days of fermentation, the lowest pH (4.23) and the lowest content of ammoniacal nitrogen (NH3-N) in dry matter (DM, 4.39%) were observed in the LP treatment. Interestingly, there was a significant (p < 0.05) difference in lactic acid (LA) concentration among the three treatments. The LP treatment had the highest lactate concentration (7.49% DM). At the same time, a markedly (p < 0.05) elevated acetic acid (AA) concentration (2.48% DM) was detected in the LB treatment. The Shannon and Chao1 indexes of bacterial and fungal communities in all the silage samples decreased compared to those in the fresh materials (FM). Proteobacteria was the dominant phylum in the FM group and shifted from Proteobacteria to Firmicutes after ensiling. Lactobacillus (64.87%) and Weissella (18.93%) were the predominant genera in the CON, whereas Lactobacillus dominated the fermentation process in the LB (94.65%) and LP (99.60%) treatments. For the fungal community structure, the major genus was Apiotrichum (21.65% and 60.66%) in the FM and CON groups after 30 days of fermentation. Apiotrichum was the most predominant in the LB and LP treatments, accounting for 52.54% and 34.47%, respectively. The genera Lactococcus, Pediococcus, and Weissella were negatively associated with the LA content. The genus Ustilago and Bulleromyces were positively associated with the LA content. These results suggest that the addition of LAB regulated the microbial community in oat silage, which influenced the ensiling products, and LP was more beneficial for decreasing the pH and NH3-N and increasing the LA concentration than LB in forage oat silage.