Relationship of Protein Level to the Minimum Lysine Requirement of the Rat

Abstract

Weanling rats were fed isocaloric diets in which corn gluten supplied 54% of the nitrogen, purified amino acids approximately 32%, and diammonium citrate approximately 14%. Except for lysine, all diets contained the proportions of essential amino acids found in whole egg protein. Minimum lysine requirements were determined at 4% increments from 8 to 24%, and at 32 and 40% crude protein. The minimum lysine requirements expressed as a percentage of the diet remained essentially constant in the protein range of 16 to 40%. Minimum lysine requirements were (in per cent) 0.54, 0.67, 0.84, 0.85, 0.86, 0.83, and 0.90 with 8, 12, 16, 20, 24, 32, and 40% of total protein (N × 6.25), respectively. Expressed as a percentage of the total protein, the lysine requirements were 6.7, 5.6, 5.2, 4.2, 3.6, 2.6, and 2.2%, respectively.