Contents of Zn, Cu, Mn and Se in Milk in Relation to their Concentrations in Blood, Milk Yield and Stage of Lactation in Dairy Cattle

The objective of the study was to assess the effect of actual daily milk production and lactation stage on concentrations of Zn, Mn, Cu and Se in milk, and monitor correlations between milk and blood concentrations of these microelements. The study was performed in it herd of Holstein cattle with the average milk yield of 8.562 kg. Thirty-five dairy cows housed in one group were included in the study. Blood and milk samples were taken during two separate milk yield checks done 4 weeks apart. Actual milk production of monitored cows ranged from 19.6 to 62.61 daily. For lactation stages we evaluated results of examinations performed from 7 to 189 days of lactation. Blood examinations showed that the cows included in our study had good supplementation with the microelements in question. Milk concentrations of individual microelements were its follows: 3855.2 + 814.7 mu g/l of Zn; 36.3 +/- 14.4 mu g/l of Cu: 20.1 +/- 8.3 mu g/l of Mn, and 28.6 +/- 7.1 mu g/l of Se. The effect of daily milk production on milk concentrations of the microelements; was identified only for copper (r -0.302, p <= 0.05). The variable of days of lactation (not considering days of the colostrum period) showed a positive correlation in manganese (r 0.419, p <= 0.01); copper and selenium showed negative correlations (Cu: r -0.258, p <= 0.05; Se: r -0.277, p < 0.05). The daily milk production influenced negatively only Cu concentration in milk, but Se, Zn and Mn was not influenced. With advancing, lactation after colostrum period the concentration of Mn in milk raised, the concentration of Cu and Se declined and the concentration of Zn was unchanged