RESUMO
The objective was to evaluate the effect of using prebiotics (Saccharomyces cerevisiae boulardii) or Monensin in the confinement initial phase and replacing monensin with probiotics (Bacillus toyonensis) in the final phase. Forty-eight Nellore steers were used, with an initial mean body weight of 356.2 ± 17.98 kg, distributed in a completely randomized design. Two animals per pen were confined in 80 m2 pens. The experiment was divided into two stages. The first phase lasted from day 1 to the 30th day, during which the animals were divided into two groups of 24 animals each. The treatments were the nutritional additives added to the diet: monensin or prebiotics (Saccharomyces cerevisiae boulardii). In the second phase, each group was subdivided into 12 animals by treatment, which received monensin or probiotics (Bacillus toyonensis). Dry matter intake (DMI), animal performance, and economic evaluation of the use of additives were evaluated. There was no additive effect on DMI, average daily gain, and total weight gain of the animals in the first experimental stage (0-30th day). Likewise, in the second stage (31st-100th day), there was no treatment effect for the variables of intake and performance. There was no effect of the use of different nutritional additives on carcass characteristics. The use of prebiotics sequentially to probiotics promoted gross and net yield that was superior to that of the animals that consumed monensin. Yeasts and bacteria respectively in the first and second phases of confinement can replace monensin in confinement diets.