Addah, W., Baah, J., Groenewegen, P., Okine, E. K. and McAllister, T. A. 2011. Comparison of the fermentation characteristics, aerobic stability and nutritive value of barley and corn silages ensiled with or without a mixed bacterial inoculant. Can. J. Anim. Sci. 91: 133–146. Barley (Hordeum vulgare L.) and corn (Zea mays) silage are the most commonly used forages in feedlot diets in western Canada, and are often inoculated in an effort to improve their preservation and quality. However, the relative value of these two forages in feedlot diets or their responses to inoculation have not previously been compared. Whole-crop barley (B) and corn (C) forage were ensiled for 63 and 77 d, respectively, in both mini silos and Ag Bags® without and with inoculation [Lactobacillus plantarum, Enterococcus faecium, Pediococcus acidilactici at 1.0×105 CFU g-1 forage; inoculated barley (IB), inoculated corn (IC)]. At the end of the ensiling period in mini silos, the pH of C and IC was lower (P<0.001) than B and IB silage, but lactate:acetate was higher (P<0.001) in IB than other silages (8:1 vs. ~4:1). Inoculation did not affect dry matter (DM) loss during ensiling, but losses in barley were higher (P<0.001) than in corn silage. Barley silage appeared to be more stable than corn after 2 d of aerobic exposure. Inoculation of barley or corn did not affect in situ organic matter disappearance (OMD) or DM intake, average daily gain (ADG) or feed efficiency of steers. However, steers fed barley silage had a higher (P=0.037) DM intake, ADG (P=0.002) and improved (P=0.002) feed efficiency compared with those fed corn silage. The inoculant was more effective at improving the fermentation and aerobic stability of barley as compared with corn, and growth and feed efficiency of cattle fed barley silage was superior to those fed corn silage.