EN
The studies were done on 86 normal (66 mares and 20 stallions) Polish Small horses at the age of above 1.5 years. Biocemical indices were determined in the sera and plasma of the blood taken from the external jugular vein at four seasons during the twoyear period of examinations. Significant differences between mares and stallions were noted in the following biochemical parameters: content of Mg, Ca, glucose, total protein, alpha and beta-globulin fractions. As a rule, higher values of these parameters were found in stallions, but these differences were not always statistically significant.