EN
The content of Mg, Zn, Cu, Mn and Co in the hairs of 24 three-year-old Great Poland mares was analyzed after summer and winter feeding. Significant differences in the content of Zn and Co were found between the winter and summer seasons. No significant differences were fround for the other elements in the analyzed seasons. The levels of Mg, Cu and Zn were lower than those shown by the other authors. On the other hand, the level of Mn and Co were higher than mean values. The content of the examined elements in hairs, like the content in blood and in the hof horn, could be treated as an index of their supply to the horses.