Effects of Lactic Acid Bacteria Inoculation on Silage Quality and Mycotoxin Levels in BYDV-Infected Oat Silage

This study investigated the effects of lactic acid bacteria (LAB) inoculants on silage quality, mycotoxin, bacterial community, and aerobic stability of barley yellow dwarf virus (BYDV)-infected oat silage. A 2 × 4 factorial design was employed using healthy (H) and naturally BYDV-infected (S) oats, consisting of four additive treatments, Lactiplantibacillus plantarum (TX), Lentilactobacillus buchneri (YX), their combination (FH), and sterile water as the control (CK), with three replicates per treatment (24 silos in total). Fermentation quality and mycotoxin content were analyzed after 75 days of ensiling and 4 days of aerobic exposure, with the day-75 bacterial community characterized. BYDV infection severely impaired raw material quality, significantly reducing water-soluble carbohydrate (WSC) content by approximately 27.0% while elevating aflatoxin (AFT), zearalenone (ZEN), and deoxynivalenol (DON) concentrations by approximately 58.8%, 44.6%, and 54.3%, respectively (p < 0.01). Microbial analysis revealed that LAB inoculation effectively restructured the fermentation microbiota, with TX increasing Lactiplantibacillus abundance, FH suppressing Enterococcus while promoting Lentilactobacillus, and YX enriching Leuconostoc. Furthermore, TX increased crude protein (CP) content and lowered pH and ammonia nitrogen levels; YX boosted acetic acid accumulation and enhanced aerobic stability post-exposure, thereby enhancing aerobic stability; and FH preserved higher dry matter, WSC, and ether extract contents (p < 0.05). In S group, TX was most effective against AFT, reducing it by 24.0–31.1%, whereas FH showed superior efficacy against ZEN and DON, with reductions of 15.1–17.4% and 13.3–16.5%, respectively (p < 0.05). Consequently, LAB inoculation improves silage quality and reduces mycotoxins in diseased forage, with L. plantarum alone or combined with L. buchneri recommended for its utilization.