After the experience of the first volume, The World Association for Animal Production (WAAP) continues the publication of the Book of the Year series for the benefit of animal scientists and policy makers in the field of livestock systems. The WAAP asked the best known and significant animal scientists in the world to contribute to the preparation of this book. Following the success of the first volume of the series, the WAAP Book of the Year 2003, many authors from the six continents are contributing to this 2nd volume. The importance of this publication is to have already established a worldwide reference for the animal science and production sectors. There are the usual four sections that raised much interest in the previous volume of the series. The first section has six articles, describing the changing conditions of livestock systems in each of the six continents. The second section has more than twenty papers, describing the development of the many sectors in which the animal science field has been divided. The third section, dealing with contemporary issues, is declared by our readers to be the most interesting. It allows participating authors to describe current and significant issues important in these last years for the animal science and production sectors. The statistics produced in the previous volume are updated and enhanced with new figures in this book to form the fourth section. The papers included in this book speak clearly of the development in the last twelve months in the livestock systems worldwide. Major space is also devoted to the list of references from where every author can start to deepen his knowledge. This book is essential for libraries that want their readers to be easily updated. Also scientists, policy makers and scientific writers, who need, to enhance their competence, to have the most practical way of knowing what is going on in the world in the field of livestock science and production will find this book of great value.