This book provides a review of the current state of knowledge on all aspects of sheep nutrition. The main emphasis is on sheep grazing in systems that range from intensively utilized sown pastures to extensive rangelands. Much of a sheep’s diet depends on grass or other forages that can be either sparse or of poor quality, so the provision of adequate dietary energy is important. Poor-quality forage, even in abundance, may not provide sufficient available energy for maintenance and production. The energy requirement of ewes is greatest during the first 8–10 weeks of lactation. Because milk production declines after this period and the lambs have begun foraging, the requirement of the ewe is then reduced to prelambing levels.