Effect of D-Alanine and D-Aspartic Acid on the Chick

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Abstract
Some effects of feeding chicks D- or L-dispensable amino acids for 2 weeks in three types (practical, purified and amino acid) of complete diets have been studied. Growth was depressed significantly by 1.5% of D-alanine, but not by 2% of L-alanine or 2% of D-serine. When the amino acid diet contained 4.4% of other D-amino acids, 1.25% of D-alanine also caused growth depression. Two percent of D-aspartic acid depressed growth significantly, whereas 6% of L-aspartic acid did not. When D-aspartic acid was replaced by L-aspartic acid after 1 week, growth rate and feed consumption increased rapidly and approached values for control birds. Plasma aspartic acid concentration, which was high when D-aspartic acid was fed returned to near normal within 2 days. Plasma free aspartic acid concentration increased to 25-fold the normal value within 3 days when the D-aspartic acid was substituted for the L-form after 1 week. A high plasma free aspartic acid concentration was maintained in chicks fed 2% of D-aspartic acid. L-Aspartic acid at 3% in the diet did not elevate plasma aspartic acid concentration. High protein (35% and 50%) diets, amino acid supplements and additional vitamins all failed to overcome the growth-depressing effect of D-aspartic acid.