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The adequate supply with essential trace elements is the prerequisite for a good performance in dairy farming. Both, a lack or a surplus lead to damage in health. In this study statements should be taken about appropriate sample media that mirror the molybdenum supply in dairy cows. Generally it is true for molybdenum that not a lack of the element leads to a jeopardizing of their clinical health but a surplus which ends up in lower milk yields and fertility rates. The study has been divided into two sections. The first section was a sample test of the molybdenum concentration of clinically health and multiparous Holstein-Frisian cows in different stages of lactation in 1400 groups on 489 dairy farms in East Germany from 2007 to 2010. Samples materials were blood plasma, blood serum, EDTA blood, urine as well as hair. In the second section the clinically health Holstein-Frisian cows of only one farm were examined. Molybdenum concentration of the sample materials (blood plasma, blood serum, EDTA blood, urine as well as hair) of 10 cows in each lactation group was determined. ICPOES and -MS of an external laboratory were used to determine the molybdenum concentration. The results were evaluated with variance analysis, regression analysis and a Bland-Altmann plot. The examination of the molybdenum supply in dairy cows in this study showed neither a lack of supply nor an intoxication. Comparing the molybdenum concentration in the sample media plasma, serum and EDTA blood, serum and plasma were equal, but significantly lower in EDTA blood. Blood samples of dairy cows showed values in the lower area of concentration (< 10 μg/l). There were no evidence of any deficiency symptoms. The reference range given by DIRKSEN et al. (2006) (50 μg/l) was overspend only a few times (0.3 – 0.5%). Renal excretion is the key regulation mechanism to avoid an acute intoxication. Molybdenum concentration in urine correlated strongly with concentrations in serum and plasma. Although ⅔ of the values came from the lower range (< 125 μg/l). Molybdenum concentration in hair showed slight correlation to urine, serum and plasma. In 35 % of the cows the molybdenum concentrations in hair were above the reference range of DIRKSEN et al. (2006) (300) μg/kg). Within the second herd test besides the blood and urine samples, liver biopsies were made additionally. Here 18% of the cows showed a molybdenum concentration above the reference range of HERDT and HOFF (2011) (4000 μg/kg TS). There were no correlations in the samples of liver tissue and blood, but a slight correlation between liver tissue and hair regarding to the molybdenum concentrations. The analytic methods (Atomic emission spectroscopy (OES-ICP) and mass spectroscopy (MS-ICP)) for molybdenum determination correlated strongly, however molybdenum concentrations measured with MS technique were higher than the OES results. Investigating geographical aspects provided for the small number of animals from Thuringia significantly lower molybdenum concentrations than in animals from the rest of East Germany. It does not allow any conclusion to the site as the food inevitably not origins from the same federal state. Molybdenum concentrations showed no significant correlations in the samples with respect to the state of lactation. In 2008 molybdenum showed significantly higher concentrations in plasma, serum and urine than for the rest of the period. The reason for this increase is unknown. In summer molybdenum concentrations were significantly lower than for the rest of the year. A possible reason could be a lower food intake besides the higher temperatures in summer. Plasma, serum and urine are short time parameters to evaluate the molybdenum supply. Taking into account the limits of the measurement method and the key role of the kidney in the regulation of molybdenum balance the urine test is particularly, with regard to the higher concentrations, well suited to detect both, a currently existing over-supply but also a lack of molybdenum. The concentrations of liver tissue gave good advice on the supply of the last months. But sampling is much more difficult than taking other sample media like blood, urine and hair. For a long-term rating of the molybdenum balance a hair analysis is less suitable because of possible exogenous contaminations. In this study the critical values of the single sample media were determined and compared with literature. Resulting from this recommendable ranges of reference were specified and given for an appropriate supply.