Therefore, the effects of Bacillus-based probiotics should be evaluated for a longer period of time. Yan et al. (2009) indicated that energy is highly associated with feed intake, which may indicate that the intake of probiotics may be affected by the energy density of the diet. Meng et al. (2010) also suggested that nutrient density could influence the effect of probiotics in growing pigs.However, to the best of our knowledge, most of the studies conducted to evaluate the effects of probiotics have used thesame dietary nutrient concentration for all treatments. The objective of this study was to investigate the effects of a Bacillus-based probiotic complex on the growth performance and apparent total tract digestibility (ATTD) of wean-to finish pigs fed diets varying in energy density.