Livestock production currently accounts for some 40% of the gross value of world agricultural production, and its share is rising (FAO, 2002). Livestock production is the largest user of agricultural land; directly through grazing of pastures and indirectly through the production of forage crops and other feeds. Over the next 20 years, there will be a massive increase in demand for food of animal origin in developing countries, and this increase will be greater than for either the major cereals or roots and tubers (IFPRI, 1995; Delgado et al., 1999).