Stress and its relationship to the occurrence of diseases have long been recognized. Stress is induced by parturition, lactation, weaning and transport, and decreases the ability of the animals to respond immunologically to antigens that they encounter. Furthermore, researches have indicated that stress can alter the metabolism of trace minerals. In this work, we investigated the mineral concentration in the serum of sheep under pharmacological induced stress. Two homogeneous groups of 6 dairy sheep each were used, one negative control (CT) and one injected with ACTH (adrenocorticotropic hormone) to mimic biological stress. The groups were fed with a restricted amount of the same basal diet. Blood samples were collected before (T0), and after 3 (T3) and 51 (T51) h from the first ACTH injection. We attempted to quantify elemental serum contents using synchrotron radiation total reflection x-ray fluorescence (SR-TXRF) at the Brazilian Synchrotron Light Laboratory. The analysis indicates that the ATCH activity causes significant variations in K, Ca, Cu and Zn concentrations. Our results indicate that stress can affect serum microelement concentrations and further analyses are required to investigate the physiological meaning of Ca and Cu variations.