AimsThis study investigated the influence of two microbial inoculants; Lactobacillus formosensis and Lactobacillus buchneri on fermentation quality, chemical composition, aerobic stability and invitro ruminal biological activity of condensed tannins in sweet potato vines silage. Methods and ResultsSweet potato vines were ensiled for 28 and 60days; without inoculant (CON), with Lact.buchneri (LB) or with Lact.formosensis (LF), both inoculants applied to achieve 1x10(6)CFUg(-1) fresh forage. Lactobacillus formosensis silage had lower pH and higher lactic acid than all treatments. Yeasts and moulds were not detected in LB silage after ensiling. Lactobacillus buchneri silage was more aerobically stable than all treatments, whereas LF was more stable than CON silage. In vitro ruminal biological activity of condensed tannins was lower in microbial-inoculated silages than CON after ensiling. ConclusionLactobacillus formosensis improved fermentability by reducing silage pH and improved aerobic stability by producing more propionate, which inhibited yeast activity. Lactobacillus buchneri improved aerobic stability of the silage by producing more acetate. Both strains effectively reduced the antinutritional effect of condensed tannins after ensiling. Significance and Impact of the StudyLactobacillus formosensis has the potential to be used as a silage inoculant because of its ability to improve fermentability and aerobic stability in sweet potato vines silage.