The history of the Oskar-Kellner-Institute in Rostock has its roots in the first German Agricultural Experimental Station in Leipzig-Mockern, Oskar Kellner's place of activities. In 1953 the Oskar-Kellner-Institute for Animal Nutrition, Leipzig-Mockern was set up. The foundation-stone for a new building of the institute in Rostock was laid in 1954. The new Oskar-Kellner-institute with four new buildings was completed in 1960. The main building placed laboratories for analyses of feed quality, investigations on protein quality by chemical and microbiological amino acid analyses and animal tests for the estimation of biological value of proteins. In the respiration building 10 respiration units for farm animals and diverse units for rats, rabbits and poultry, were built up to study feed utilization and energy requirement of different animal categories with divergent productivities as well as the physiological background of energy metabolism. A third building served for feeding trials and forage preservation. The purpose of a fourth building was to analyze exponents using isotopes especially in studies on protein metabolism. Overall objective of the research was to establish the basis for developing a system of feed evaluation and feed requirement of animals with different productivity. The information obtained by feed analyses, energetic efficiency of feed utilization, protein quality, energy and protein requirement of animals etc. provided the fundamentals of the Rostock Feed Evaluation System, first edition in 1971. All divisions of the Oskar-Kellner-Institute and further institutes contributed to this book. The system has been continuously underwent improvement and completion up to date.