Determination of Essential and Toxic Elements in Raw Sheep's Milk from Area of Slovakia with Environmental Burden

Concentrations of selected essential (Ca, Mg, Zn, Se, Fe, Cu) and toxic elements (As, Cd, Hg, Pb, Ni) were analyzed in milk of sheep (300 ewes of Tsigai breed) depending on lactation stage in area of Slovakia with slightly disturbed environment. To determine the real state of environment in the selected area, the study was extended to include analyses of the soil and animal feed (green pastures). Analyses of elements in soil were performed using ICP-OES and elements in feed and milk using the AAS-HG, AES-ICP, AAS-ETA, AAS-AMA, and AAS-F. Analyses of soil samples and feed samples revealed the presence of toxic elements in this area, but their concentrations did not affect concentrations in milk and were below the LOQ (limit quantification). Significant decrease of Ca as well as Mg and Zn (P < 0.05) concentrations was found between early and middle stages of lactation and significant increase between the middle and late of lactation period. Concentration of Se and Fe in milk during the lactation significantly increased (P < 0.05) in the last stage of lactation. Concentration of Cu in milk of sheep was below LOQ during all stages of lactation. In the milk of sheep during the lactation stages, the significant positive correlations between concentrations of the following elements were observed: Ca-Mg, Fe-Se, Ca-Se, Ca-Fe, Mg-Se, Mg-Fe, Ca-Zn, and Mg-Zn. The low concentrations, below LOQ of selected toxic elements in milk of ewes, indicate the safety of this milk for direct consumption or for further food processing.