Effect of Excess Dietary L-, DL- and D-Serine on the Chicks1

ABSTRACT A series of experiments were conducted to study the effectsof excessdietary L-, DL- and D-serine on growth and blood serine concentration in the chick. Day-old chicks (N.H.XS.C.W.L.) were fed either an L-amino acid diet or a practical diet containing various amounts of serine for two weeks. At the end of the experiment, the blood was taken for the determination of plasma or serum free serine. The growth of chicks was significantly depressed when 2.86 % L-serine was included in the L-amino acid diet or in the practical diet. Severe growth depression and mortality were ob-served when dietary L-serine exceeded the 4 % level. The addition of excess folic acid, vitamins B6 and B12 (20XN.R.C. requirement) to the practical diet containing 4 % L-serine was able to correct partially the growth depression effect caused by excess dietary serine, but was unable to restore the growth of chicks to the controls. DL-serine was less harmful to the chick at the level corresponding to that of L-serine. D-serine fed at the 4 % level had a slight growth inhibi-tion on the chick. The level of serine in the plasma or serum was increased with the increases of dietary serine content. An extremely high concentration of serine was observed whenever there was a severe growth depression. D-serine was absorbed and metabolized in the chick