Rate of Respiratory Carbon-14 Dioxide Excretion after Injection of C14-Amino Acids in Rats Fed Raw Soybean Meal

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Abstract
Weanling rats were fed heated or raw soybean meal rations, and C14-amino acids were administered by intraperitoneal injection. The rate of respiratory C14 dioxide excretion was followed. The rates noted were typical asymptotic plots except following the injection of threonine or valine in animals fed raw soybean. In the latter, the plots showed 2 distinctly different characteristics: 1) the initial rate of C14 dioxide excretion was lower and, 2) the rate increased markedly at 4 to 5 hours after injection. The hypothesis was presented that the raw soybean growth inhibitory factor(s) was acting as a block to threonine and valine catabolism and that its effect was dissipated some 4 to 5 hours or more after feeding as the animals did not have access to food during the collection period.