Abstract There has been a dogma that milk cannot provide adequate zinc requirements of calves in the first days of their life. This study was performed to determine whether zinc supplementation of the diet of neonatal dairy calves could promote a healthy hematology, biochemistry, growth rate and health. Thirty three Holstein calves were divided equally into three groups (control, test group 1, and test group 2). The dietary, environmental, and husbandry factors were similar in all groups. Zinc (50 ppm) as ZnSO4 was added to each milk meal of test group 1 and 100 ppm ZnSO4 was added to each milk meal of test group 2 for 14 days. No zinc sulfate was added to the diet of the control group. Blood samples were collected from the jugular vein 24 h–48 h after birth and at the end of the first, third and sixth weeks of life for measuring hematological and biochemical parameters including aspartate transaminase (AST), alkaline phosphatase (ALP), iron (Fe), calcium (Ca), phosphorus (P), albumin (Alb), total protein (TP), globulin (Glb), and glucose (Glu). Daily weight gain, total weight gain, and days of treatment during the study were also recorded. Statistical analysis indicated that the levels of total protein and albumin at 6 weeks in test group 2 were significantly higher than test group 1. Calcium at 6 weeks in test group 2 was significantly higher than test group 1 and controls. Glucose at 6 weeks in controls was significantly higher than test group 1. AST in test group 1 and globulin in test group 2 at the first sampling time were significantly higher than controls. No significant differences were observed among groups for other parameters.

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