The content of energy in horse feeds is more difficult to grasp. This is due partly to the fact that we can express the energy requirements for horses both in megajoules and feed units. In addition, energy demands and the energy content of horse feeds may also be calculated in different ways: i.e. as digestible energy, metabolisable energy, or net energy. We will return to this later, since it has practical significance, because the method of calculation of energy varies from country to country, and is in large part based on the traditions of different countries. As long as we calculate energy requirements and feed energy content in the same way, however, the horse will get the right amount of energy. We have taken this into account in the PC-Horse program.