ABSTRACT The aim of study was to determine the impact of a probiotic preparation containing live bacteria Bacillus cereus var. toyoi on the performance of turkeys in order to define the effective dose of the preparation and to evaluate its influence on poults' livability in the first month of life. Three hundred and sixty B.U.T. 9 male turkey were divided into three groups. The control group (I) was fed a diet with no probiotic additive, and groups II and III were given a probiotic product containing 0.2x109 and 1x109 B. toyoi CFU/kg of feed respectively. Body weight was recorded in weeks 1, 6, and 18. Livability, feed conversion ratio, and European Efficiency Factor (EEF) were estimated. In experiment II, the impact of a standardized probiotic dose on livability and performance parameters of B.U.T. 9 turkey poults were evaluated. Two groups were selected within each sex: control (C), feed without probiotic, and experimental (T), which feed contained the probiotic preparation. Mortality and body weight were registered. The better livability and performance of the turkeys fed probiotic justifies the use of bacteria Bacillus cereus var. toyoi to improve performance results and livability during the first weeks of the turkeys' life. The bacterium strain concentration of 1.0x109 CFU/kg of feed can be assumed as optimal.