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.

摘要

The objectives of this study were to assess the effect of actual daily milk production and lactation stage on the concentrations of Zn, Mn, Cu and Se in milk and to monitor the correlations between milk and blood concentrations of these microelements. This study was performed in a herd of Holstein [Holstein-Friesian] cattle with an average milk yield of 8562 kg. A total of 35 dairy cows housed in one group were included in the study. Blood and milk samples were taken during 2 separate milk yield checks done 4 weeks apart. The actual milk production of monitored cows ranged from 19.6 to 62.61 daily. For lactation stages, the results of examinations performed from 7-188 days of lactation were evaluated. Blood examinations showed that the cows included in this study had good supplementation with the microelements in question. Milk concentrations of individual microelements were as follows: 3855.2+or-814.7 micro g/litre of Zn; 36.3+or-14.4 micro g/litre of Cu; 20.1+or-8.3 micro g/litre of Mn; and 28.6+or-7.1 micro g/litre 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 with Mn (r=0.419, p<=0.01). Cu and Se showed negative correlations (Cu: r=-0.258, p<=0.05; Se: r=-0.277, p<=0.05). The daily milk production negatively influenced only the Cu concentration in milk, but Se, Zn and Mn were not influenced. With advancing lactation after colostrum period, the concentration of Mn in milk increased, the concentration of Cu and Se declined and the concentration of Zn was unchanged.