EN
The aim of the study was to explain why in a farm in the Bydgoszcz region young cattle were getting low body weight gains and milking cows were in a poor state of health. The studies included blood assessment, i.e. haematocrit - Ht, concentration of haemoglobin - Hb, the level of Cu and ceruloplasmin - Cp in sera obtained from the animals treated by various systems during grazing time and following feeding on silage supplemented with microelements. Iron metabolism was assessed on the basis of the changes of Fe levels, total iron bunding capacity (TIBC), unsaturated iron binding capacity (UIBC) in sera and the index of transferrin saturation (TfS). The studies indicated that lowered indices of Ht and Hb during grazing time were accompanied by hypocupraemia. Despite low concentrations of Cp in sera of cows with hypocupraemia, the alterations in Fe, UIBC and TfS pointed to a mobilisation of iron transport.