The experiment was carried out on 40 Polish Black-and-White HF bull calves (52-87% of HF blood) aged from 9 and 12 days at the beginning of the experiment to 90 days at its end. From the beginning of the trial the calves were offered restricted liquid feed to 56 days of age and concentrates ad libitum according to IZ-PIB-INRA recommendations. The concentrates were without sodium butyrate (control group, C), or with 1% Na-butyrate (group B1), 3% Na-butyrate (group B3) and 0.3% Na-butyrate (group B0.3), and included meadow hay from 0.10 kg/day during the liquid feeding period to 0.20 kg/day after weaning at 57 days of age. Na-butyrate at 3% in the diet reduced feed intake and had a beneficial effect on calf growth and nutrient utilization. The dietary level of Na-butyrate did not cause significant changes in serum β-hydroxybutyric acid concentration of the calves.