32 neonatal Black Pie dairy calves (22 females and 10 males), clinically healthy, in a farm from Romania were divided into 8 groups according to age (group 1= one day old, group 2= 2 days old, group 3= 4 days old, group 4= 8 days old, group 5= 11 days old, group 6= 18 days old, group 7= 24 days old and group 8= 29 days old) and blood sampled to investigate the changes in the concentrations of serum total protein (PT), albumin (Alb), globulin (Gb), iron (Fe), ceruloplasmin (Cerlp) and plasma haptoglobin (Hapt); the haematological variables measured were: red blood cells (RBC), haematocrit (Htc), haemoglobin (Hb), mean cell volume (MCV), mean cell haemoglobin (MCH), mean cell haemoglobin concentration (MCHC), platelets, reticulocytes, white blood cells (WBC), lymphocytes, monocytes, neutrophils, eosinophils and basophils. The values are discussed in relation to the published reference ranges for adult cattle. In the present study, Pearson correlation test showed a positive association between ceruloplasmin and RBC, Hb, Htc (P = 0,001) and globulin (P = 0,004) values. Also Pearson correlation test showed a negative association (P = 0,04) between ceruloplasmin values and number of platelets. There were significant age related changes (p < 0,05) for MCV, MCH, MCHC, platelets, WBC, neutrophils, lymphocytes, neutrophils. total protein and globulin values. Serum ceruloplasmin were below cattle reference range 120-200 mg/L for all 32 calves. The results help to indicate when the use of the adult haematological and biochemical reference ranges is inappropriate and to act as a guide to the values to be expected in younger animals.