Seventy heifer calves were used to evaluate the effects of a postbiotic supplement on growth performance and blood metabolites from birth to wk 18 at a commercial dairy farm in South Dakota. After birth calves were assigned to: 1) Control with no supplement (CON; n = 35) and 2) supplemented with 3 g/d Probisan in milk from birth to weaning, and 1.5 g/kg concentrate mixture after weaning (PRO; n = 35). All calves were fed 2.6 L per meal until wk 8 (weaning transition). A commercial starter was fed ad libitum from d 14 and hay and concentrate mixture after weaning. Body weight, hip width and intake were individually recorded (weekly, biweekly and daily; respectively). Blood was drawn biweekly from birth to measure plasma concentrations of glucose, BHB, and triglycerides. Data were analyzed as a completely randomized design with repeated measures using mixed models (SAS 9.4). No differences were detected (P > 0.10) between groups for average body weight (71.8 ± 0.9 kg), growth rate (785 ± 11 g/d), or hip width (20.1 ± 0.1 cm). Groups consumed similar (P > 0.10) amount of starter from wk 3 to 5 (226 ± 67 g/d), but from wk 6 to 10, PRO calves consumed less (P = 0.043) amounts (CON = 926 ± 51 and PRO = 804 ± 50 g/d). Glucose (103.5 ± 1.21 mg/dL), BHB (0.648 ± 0.035 mmol/L), and triglycerides (13.20 ± 0.71 mg/dL) did not vary (P > 0.10) between groups and no interaction between treatment and week. However, metabolites changed (P < 0.001) throughout time where glucose decreased from 110.4 to 93.7 mg/dL (wk 0 to 6 and 10 to 18, respectively), BHB increased from 0.448 to 1.015 mmol/L (wk 0 to 6 and 10 to 18, respectively), and triglycerides were highest at wk 0 (21.77 mg/dL) and lowest at wk 18 (7.46 mg/dL). These changes were in accordance with the milk consumption reduction and the development of rumen functions throughout time. In conclusion, despite the lower consumption of solid feeds intake from wk 6 to 10 by PRO calves, no differences were detected in growth performance. Blood metabolites were similar between groups and their pattern change over time indicated similar rumen development. Study supported by Pentabiol, Spain.