This book is intended to provide an in-depth and comprehensive analysis of our current and available knowledge on four basic aspects of feeding animals under grazing conditions and some alternatives to improve food production from animals. Those are, namely, grasses, grasses and the environment, grazing systems and animal performance under grazing conditions, and what should be done to stop polluting our environment. Furthermore, this book will include information related not only to ruminants but also to non-ruminants used worldwide for food production. In Section I, information on natural and introduced grasses, methods, and philosophies on grazing systems will be reviewed. Section II will review the information on the effects of climate (temperate vs. tropical) on grass and forage production. Section III will review the information on strategies and methodologies as it applies to animal production under grazing conditions. Finally, the information on the effects of genetics and biotypes of animals on food and other items in production will also be reviewed. It must be clearly emphasized that this book will have two implicit features- one being that of efficiency of production and the second being of sustainability and preservation of the environment.