Oat is a forage with high protein value (10–14% DM) and good palatability, and is considered one of the main feed sources for ruminants. In this experiment, Lacticaseibacillus rhamnosus and Lentilactobacillus buchneri were selected as silage additives to investigate the fermentation quality, nutrient composition, microbial community and relationship between fermentation products and bacterial community of small-bale oat silage after ensiling. The experiment was set up with three treatment groups and three replications in each group, which were the control (C) group, L. rhamnosus (LR) group and L. buchneri (LB) group, and oat silages were subjected to 10-day and 30-day storage periods. The results show that both LR and LB additions significantly increased water-soluble carbohydrate, crude protein, lactic acid, propionic acid and acetic acid contents, and decreased pH, butyric acid, acid detergent fiber, neutral detergent fiber, and ammonia nitrogen contents and yeast and enterobacteria numbers in small-bale oat silage, compared with the C group. The highest content of acetic acid and the lowest numbers of enterobacteria and yeast were found in the LB group after 30 days of fermentation. Lentilactobacillus and Lacticaseibacillus were the dominant genera in the LB and LR groups, regardless of fermentation time. Lentilactobacillus and Lacticaseibacillus were positively correlated with a correlation value of 0.9, but both were negatively correlated with Bacillus. Lentilactobacillus and Lacticaseibacillus were positively correlated with acetic and lactic acids, while pH and butyric acid were positively correlated with Bacillus. This experiment revealed that the addition of homofermentative and heterofermentative lactic acid bacteria enhanced the relative abundance of Lentilactobacillus and Lacticaseibacillus, reduced harmful microbes, and improved fermentation quality of small-bale oat silage.

The purpose of this study was to investigate the effect of different additives on the microbial composition, fermentation quality, and bacterial community structure of big-bale Leymus chinensis silage. An experiment was set up with four treatment groups: a control (C) group, Lacticaseibacillus rhamnosus (L) group, molasses (M) group, and L. rhamnosus + molasses (LM) group, with three replications per group, and L. chinensis silages were fermented for 20 and 40 days. The lactic acid, acetic acid, 1,2-propanediol, and propionic acid contents increased, and pH, butyric acid, 1-propanol, and ethanol contents decreased in the L, M, and LM groups compared to the C group. In the LM group, the number of lactic acid bacteria was the highest, while the pH was the lowest. Enterobacter and Paucibacter were the main dominant genera in the C group. The addition of L. rhamnosus and molasses increased the relative abundance of Lactobacillus, Weissella, and Enterococcus. Lactobacillus abundance correlated positively (p < 0.01) with Lactococcus, Enterococcus, and Weissella and correlated negatively with Enterobacter and Paucibacter. Conversely, Enterobacter and Paucibacter showed a strong positive correlation (p < 0.01, R = 0.55) during fermentation. Lactobacillus, Enterococcus, and Weissella were positively associated (p < 0.01) with acetic and lactic acid levels, while Enterobacter abundance was correlated positively (p < 0.05, R = 0.43) with 1,2-propanediol content. In summary, the addition of both L. rhamnosus and molasses improved the fermentation quality and bacterial community structure of big-bale L. chinensis silage. In addition to inhibiting harmful microorganisms, this combination improved the fermentation products of big-bale L. chinensis silage through microbial regulation.