Haematology of foals up to one year old

Packed cell volume, haemoglobin concentration, erythrocyte counts, erythrocyte indices, serum iron, iron binding capacities, total and differential leucocyte counts, platelet counts, total plasma protein, fibrinogen, haptoglobin and icterus index values were determined at 14 different ages in eight Thoroughbred and 14 Quarterhorse foals during the first year of life. Absolute neutrophil numbers in blood decreased and lymphocyte numbers increased during the first months. Absolute eosinophil numbers tended to increase until three months old. Haemoglobin concentration and packed cell volume decreased significantly during the first two weeks and generally stayed in the lower portion of adult horse normal ranges during the remainder of the first year. Mean cell volume decreased to minimum values at approximately four months and then gradually increased. Serum iron was high at birth and decreased rapidly to a minimum at three days old. Total iron-binding capacity increased to a maximum at one month. Serum haptoglobin was generally within the adult normal range at birth. A moderate, but significant, decrease occurred at one week old. Fibrinogen concentration increased to a maximum at five months. Icterus index values decreased rapidly during the first two weeks of life. Minor changes occurred in other parameters measured. Possible causes for the various changes in haematological parameters are discussed.