The primary feeds for sheep are renewable and contain high concentrations of components that are not suitable for human consumption, making sheep farming sustainable. In some economies, maize, barley, sorghum, wheat, soya beans, rapeseed and their by-products are inexpensive enough to be fed strategically during some stages of the life cycle of sheep. This chapter provides a general overview of sheep nutrient requirements, discusses the measurable components of sheep feeds that supply those nutrients (including fermentable fibre), and suggests practical methods of combining feed ingredients to achieve functional supplements and diets.