This research consists of three experiments whose general objective was to evaluate the inclusion of a yeast inoculum (YI) and fermented apple bagasse (BMZN) in the diet of preweaned calves and its effect on in vitro digestibility, productive behavior and animal health. In the first experiment, the effect of an IL and BMZN in the diet of growing Angus calves on productive behavior and immune system was evaluated. The variables of the behavioral test were analyzed with a statistical model that included treatment as a fixed effect; for the immune system variables, treatment and sampling were included as fixed effects; and the animal as a random effect.