the latest information on nutrient metabolism and the formulation of diets from an array of available feedstuffs. The authors discuss animals' role in ecological balance, environmental stability and sustainable agriculture and food production. A new chapter on Regulation of Nutrient Partitioning offers a lively and timely discussion of emerging technologies in modifying and increasing efficiency of nutrient metabolism and animal food composition. A new chapter on Toxic Minerals in the Food Chain addresses the role of agricultural production animal nutrition in protecting the environment from toxic levels of minerals and nitrogen in the food chain.