Insights into Nutrient Contents, Fermentation Profiles, Bacterial Communities and Co-Occurrence Network of Small-Bale Oat Silage Prepared with/Without Lentilactobacillus buchneri or Lacticaseibacillus rhamnosus

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, <i>Lacticaseibacillus rhamnosus</i> and <i>Lentilactobacillus buchneri</i> 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, <i>L. rhamnosus</i> (LR) group and <i>L. buchneri</i> (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. <i>Lentilactobacillus</i> and <i>Lacticaseibacillus</i> were the dominant genera in the LB and LR groups, regardless of fermentation time. <i>Lentilactobacillus</i> and <i>Lacticaseibacillus</i> were positively correlated with a correlation value of 0.9, but both were negatively correlated with <i>Bacillus</i>. <i>Lentilactobacillus</i> and <i>Lacticaseibacillus</i> were positively correlated with acetic and lactic acids, while pH and butyric acid were positively correlated with <i>Bacillus</i>. This experiment revealed that the addition of homofermentative and heterofermentative lactic acid bacteria enhanced the relative abundance of <i>Lentilactobacillus</i> and <i>Lacticaseibacillus</i>, reduced harmful microbes, and improved fermentation quality of small-bale oat silage.