Micro Mineral Concentrations of Dairy Cows in Selected Areas from Slovak Republic

The aim of study was evaluation of the quality of feeds for dairy cattle on the content of copper and zinc from two agro-ecological zones (western Slovakia and eastern Slovakia). Feed samples-corn silage (n=70), lucerne silage (n=32), grass silage (n=25), and total mixed ration for dairy cows-TMR (n=66) came from livestock farms. The Cu and Zn contents were assessed in samples using atomic absorption spectrophotometer (AAS). Higher average values of zinc were found in lucerne silage from eastern Slovakia (75.04 mg/kg), in other silage were the concentration of zinc in range from 51.77 to 58.13 mg/kg. The lowest average values were found of copper in silages-corn, lucerne and grass (9.80; 9.67 and 8.10 mg/kg), respectively. In the TMR was detected the higher average content of Zn in production phases, before calving 100.43 mg/kg, after calving 109.35 mg/kg and on the top of lactation 105.29 mg/kg. A total of 396 blood serum samples were collected from 22 farms of cattle. In western Slovakia, the percentage of animals deficient in serum Zn and Cu were observed in all production phases. The levels of Zn in serum were lower than the critical level 45.07% before calving and 38.03% after calving. The serum concentration of Cu were higher at after calving 33.8% and at top lactation 33.33% of the total number of analyzed samples. In eastern Slovakia, the levels of Zn and Cu in serum samples were lower. Of the total number of samples, the amounts of Cu in serum were reduced in all production phases (before calving 14.20%, after calving 7.81% and top of lactation 16.33%. Similarly, the amount of Zn in serum was reduced (10.65%, 19.17% and 12.78%, respectively).