Effects of Biological Additives on the Fermentation Quality and Microbial Community of High-Moisture Oat Silage

The primary objective of this study was to explore the effects of biological additives, including Streptococcus bovis (SB), Bacillus subtilis (BS), xylanase (XT), and their combined treatments, including SB + BS (SBBS), SB + XT (SBXT), and BS + XT (BSXT), on the chemical composition, fermentation characteristics, and microbial community of high-moisture oat silage. Compared with the CK group (control group without additives), SB and SBBS treatments increased the lactic acid content (p < 0.05) and reduced the contents of acetic acid, propionic acid, butyric acid, and ammonia nitrogen in silage (p < 0.05). XT, SBXT, and BSXT treatments decreased the neutral detergent fiber and acid detergent fiber contents (p < 0.05), increasing the water-soluble carbohydrate content (p < 0.05). The SB, SBBS, and SBXT treatments increased the abundance of Lactiplantibacillus (p < 0.05) and significantly decreased microbial richness with diversity (p < 0.05), improving the microbial community structure in silage. The addition of XT increased the relative abundance of Clostridium and Enterobacteriaceae, but its combination with SB and BS increased the abundance of Lactiplantibacillus and inhibited the development of undesirable bacteria. Moreover, different additives changed the metabolism of carbohydrates, amino acids, energy, cofactors and vitamins of bacterial communities during ensiling. In summary, the addition of SB and SBBS was more conducive to improving the fermentation characteristics of oat, while XT, SBXT, and BSXT performed better in degrading lignocellulose in plants.