Utilization of Amino Acids from Foods by the Rat I. Methods of Testing for Lysine

Abstract

Techniques were developed for determining the quantitative utilization of lysine from purified proteins and foods, using the protein-depleted rat as the test animal. Rations that contained purified amino acids or sesame meal plus diammonium citrate and certain amino acids were used as the basal rations deficient in lysine. The weight gain of the depleted rats fed these basal rations plus graded levels of lysine, or known levels of lysine in foods, was used as the basic criterion for estimating the lysine utilization from foods. The repeatability of the results in experiments replicated with time, with the use of different levels of the test product, or with different basal rations, indicated that this approach could be used for studying the utilization of amino acids from foods. The limitations of the methods are also discussed.