Research has shown that organically reared cattle in Flanders has a number of mineral deficiencies, especially if it is not supplemented. Organic farming, however, revolves around the sustainable use of resources, and external supply of minerals should therefore be minimal. This project aims to determine whether the efficiency with which minerals are used in dairy rations can be increased by improving the bioavailability of these minerals. We want to especially look for the dietary factors (other than the concentrations of the relevant minerals) that affect mineralenbiobeschikbaarheid, and thus can provide a strategy to farmers to prevent mineral deficiencies.