The aim of this experiment was to test the effects of both dietary trace element supplementation and the stage of lactation on the milk yield per milking and the major milk components, as well as the blood concentrations of total Ca, P, Mg, Na, and K in lactating donkeys. Over a 3-month period, 16 clinically healthy lactating donkeys were used to collect milk and blood samples and to evaluate the milk yield per milking. The experimental subjects were randomly divided into two homogeneous groups, control (CTL) and trace element (TE). The donkeys in the TE group were fed a diet supplemented with Zn, Fe, Cu, Mn, Se, Co, and I. The dietary treatment did not significantly affect neither the milk yield per milking nor the milk macro ingredients. However, these variables were significantly affected by the stage of lactation. The serum concentrations of total Ca, P, Na, and K were not affected by the dietary treatment, but the serum Mg level in the TE group was significantly higher than that in the CTL group (26.6 vs. 25.0 mg/L). The effect of stage of lactation was found to be significant for all the investigated minerals in the blood serum, and negative trends were observed for serum Ca, P, Mg, Na, and K during the experimental period.