This book contains key contributions to the Xth International Symposium on Ruminant Physiology. Proceedings from past ISRP symposia have had a major influence on research and teaching in animal science over the years. Without a doubt the peer-reviewed chapters in this book, written by some of the best scientists in the field, will live up to this fine tradition. The chapters cover a wide range of topics spanning from digestion and absorption to metabolism, reproduction and lactation. Advancement of knowledge within important issues related to rumen fermentation, absorption mechanisms and splanchnic metabolism is treated in nine chapters. A number of chapters address the relationship between nutrition and gene expression illustrating important progress in scientific knowledge that can be obtained by applying the molecular biology methods to the field. Several chapters address the effects of nutrition on immunology and cover topics related to the health and welfare of production animals. In keeping with the increased attention on the relationship between food and human health, the book contains two important chapters on this topic.