The study of trace elements has gained a significant importance due to their role in plant, animal and human nutrition. Dietary trace elements are those inorganic constituents of food which are required by the body in very minute quantities. It has been proposed that they should be defined quantitatively as elements present at less than 100 ppm. In fact many trace elements are present in animal body at levels much lower than this. Generally the trace elements are embedded in trace enzymes and proteins which are implicated in health and productivity of the animals. The transfer of trace minerals through animal products is also important for human nutrition. This book contains the findings of a controlled experiment with periparturient dairy cows supplemented with various sources of dietary selenium, and a survey of some selected trace elements (selenium, zinc, copper, manganese and iron)in large dairy herds in Saxonia, Germany. Issues like dietary recommendations and practical levels,various tissue concentrations and selenium transfer from cows to calves and milk have been discussed in the book. Interactions of various trace elements have also been mentioned.