This study investigated the effects of an inoculant on silage fermentation, aerobic stability, and the growing and finishing performance of feedlot steers. Whole-crop barley (Hordeum vulgare L.) was chopped, wilted [350-400 g kg^-1 dry matter (DM)], and ensiled without (Control) or with (Treated) a bacterial inoculant containing a mixture of Pediococcus pentosaceus, Lactobacillus plantarum, and Propionibacterium freudenreicheii (1.3 × 105 CFU g^-1 forage), as well as enzymes applied to fresh forage ensiled in mini or Ag-Bag^® silos. Inoculation resulted in a pH decline (P < 0.05) from 6.0 on the day of ensiling to <4.0 after 3 d. In contrast, it required more than 20 d for the pH of the Control silage to fall below 4.0. Inoculant reduced (P < 0.05) the concentration of acetic acid and aerobic stability of silage, as evidenced by a higher (P < 0.05) temperature and pH in aerobically exposed silage. Although the inoculant accelerated pH decline during ensiling, it did not improve the growth performance (P < 0.05) or alter the carcass traits of steers. It is possible that a reduction in the aerobic stability of the inoculated silage may have contributed to this outcome.