EN
Examinations were carried out on 12 clinically normal Polish ponies at the mean age of 7 years and body weight 380-410 kg at mating season (3 months) in April-June. Six stallions received СаСОз (experimental group) for 30 days, six non-treated ones served as a control. Both experimental and control animals were fed identical natural fodder. A diet composed of 2 kg of bruised oat and 5 kg of hay contained 23.96 mg of Zn, 3.76 mg of Cu, 3.96 of Ca (control) and 12.49 mg of Ca (experimental group) per 1 kg. The following parameters were determined; total number of red blood cells, leukocytes, hemoglobin, hematocrit, total protein, activity of plasma alkaline phosphatase, level of Zn, Cu and Ca in blood sera and in hairs. It was found that calcium exess in the fodder decreases significantly the content of Zn in the blood plasma and the hairs of the stallions.