Threonine, tryptophan and histidine requirements of immature beagle dogs.

The threonine, tryptophan and histidine requirements of growing male Beagle dogs were determined using diets containing the equivalent of 14% protein as crystalline L-amino acids. For each amino acid the requirement was taken to be the minimum dietary quantity required for optimal growth, feed efficiency and nitrogen retention. In experiment 1 the threonine requirement was found to be provided by 0.52% or more dietary threonine. In experiments 2 and 3 the minimal dietary tryptophan and histidine requirements of immature dogs were estimated as 0.17 and 0.21%, respectively. The requirements for threonine and tryptophan are similar to those for growing rats. However, the histidine requirement of Beagles appears to be lower than that of rats.