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Simple Summary: Dry matter loss (DM loss) occurs during silage production, with the potential to reach up to 4–20% due to the aerobic respiration. Lower water-soluble carbohydrates (WSC) and a higher buffering capacity can contribute to this; however, the presence of Bacillus can help create an anaerobic environment, which is more conducive to the growth of anaerobic bacteria. The objective of this study was to evaluate the potential of Bacillus coagulans (BC) as an inoculant for silage fermentation. The results showed that adding BC increased the fermentation quality of alfalfa silage, especially when applied together with Lactobacillus plantarum (LP). This was evidenced by a reduction in the neutral detergent fiber (NDF) and acid detergent fiber (ADF) contents, as well as an increase in Lactobacillus abundance and a decrease in Enterococcus abundance after 60 d of fermentation. Additionally, the application of LP, BC, and their combination stimulated cofactor and vitamin metabolism abundance, whilst suppressing drug resistance: antimicrobial pathway abundance. Thus, BC could be considered a viable bioresource for improving fermentation quality. This study aimed to investigate the potential of Bacillus coagulans (BC) as an inoculant in alfalfa silage fermentation. Fresh alfalfa was harvested at a dry matter (DM) content of 329.60 g/kg fresh weight (FW), and inoculated without (CON) or with BC (1 × 106 CFU/g FW), Lactobacillus plantarum (LP, 1 × 106 CFU/g FW), and their combinations (LP+BC, 1 × 106 CFU/g FW, respectively). Samples were taken at 3, 7, 14, 30, and 60 d, with three replicates for each. The prolonged ensiling period resulted in a decrease in pH values and an increase in lactic acid (LA) concentrations in alfalfa silages. After 60 d of fermentation, the application of BC and LP decreased the pH values and increased LA concentrations in treated silages, especially when their combination was applied. Application of BC preserved more water-soluble carbohydrates (WSC), and further application of BC increased WSC in LP+BC-treated silage compared to LP-treated silage. There was no significant difference in the crude protein (CP) content between the CON and treated silages, however, the BC and LP treatments reduced the ammonia nitrogen (NH3-N) concentration, especially when their combination was applied. Additionally, the BC and LP-treated silages had lower neutral detergent fiber (NDF) and acid detergent fiber (ADF) when compared to the CON silage (p < 0.001). Inoculants also increased Lactobacillus abundance and decreased Enterococcus abundance after 60 d of fermentation. Spearman's rank correlation analysis revealed a positive correlation between LA concentration and Lactobacillus abundance. It was noteworthy that LP, BC, and their combination increased the relative abundances of carbohydrate metabolism, energy metabolism, cofactors, and vitamin metabolism, decreasing the relative abundances of amino acid metabolism and drug resistance: antimicrobial. Therefore, the inclusion of BC increased the fermentation quality of alfalfa silage, with the optimal combination being LP+BC. According to the findings, BC could be considered a viable bioresource for improving fermentation quality. [ABSTRACT FROM AUTHOR]

Simple Summary: The depressed appetite at parturition might induce the changes in the composition and quantity of rumen microbiota. At present, little is known about the influence of parturition on the levels of rumen microbiota and their fermentation ability in dairy cows. The objective of this study was to evaluate the effects of parturition on composition and quantity of bacterial communities and concentrations of short-chain fatty acids (SCFAs) with 16S rRNA high-throughput sequencing and targeted GC–MS/MS metabolomics. The results showed that parturition altered the levels of rumen bacteria and their fermentation ability. The findings provide a better understanding of the effect of parturition on rumen digestive function. The rumen fluids from ten cows at Day 3~5 before calving and Day 0 after calving were collected to analyze the composition and quantity of bacterial communities and concentrations of SCFAs. The results showed that the relative abundances of unidentified Lachnospiraceae, Acetitomaculum, Methanobrevibacter, Olsenella, Syntrophococcus, Lachnospira, and Lactobacillus genera were significant increased (p < 0.05), while that of unidentified-Prevotellaceae was notably decreased after calving (p < 0.05). In addition, the concentrations of acetic acid, propionic acid, butyric acid, and caproic acid obviously decreased after calving (p < 0.01). Our findings show that parturition altered the rumen microbiota and their fermentation ability in dairy cows. This study defines a rumen bacteria and metabolic profile of SCFAs associated with parturition in dairy cows. [ABSTRACT FROM AUTHOR]