The effects of the product ‘ZooLac Bovimix’ on the gastrointestinal tract of rosé veal calves before weaning were investigated. The product contained live yeast (Saccharomyces cerevisiae) and a postbiotic from Lactobacillus acidophilus. Twelve calves were randomly allocated to a control diet (CON; 20.8 ± 1.5 days of age and 53.8 ± 3.8 kg body weight) and twelve calves were allocated to a treatment supplemented with the product in the milk replacer and concentrate (PRO; 23.7 ± 1.8 days of age and 52.8 ± 0.9 kg body weight) for three weeks. The CFUs of yeast were 7.88 x 10⁹ and 2.38 x 10⁹ per kg milk replacer and concentrate as feed, respectively. The number of some microbiota groups, concentration of organic acids, and biogenic amines in digesta from the mid-small intestine and mid-colon were measured. In PRO group significantly higher numbers of yeast cells in both the small intestine and colon in comparison to CON group were noted. Additionally, PRO group tended (P = 0.06) to have a lower number of Clostridium perfringens in the colon. In both the small intestine and colon, concentrations of the individual and sum of organic acids were unaffected by the treatment. The concentrations of the individual biogenic amines in the small intestine and colon were also unaffected by the treatments. However, PRO group tended to have a lower total concentration of biogenic amines in the colon (P = 0.06). So, the supplementation of the product had only minor effects on the gastrointestinal tract of pre-weaned rosé veal calves.