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Journal of Nutrition Vol. 60 No. 1 September 1956, pp. 47-63
Copyright © 1956 by American Society for Nutrition
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Utilization of D-Tryptophan by the Chick1

W. D. Morrison, T. S. Hamilton and H. M. Scott

Illinois Agricultural Experiment Station, Urbana

The utilization of orally administered D-tryptophan was studied using growth as the criterion. A diet containing approximately 0.036% of tryptophan was supplemented with graded levels of the D isomer. The results suggest that D-tryptophan, if added to the diet of the young chick in sufficient quantity, will promote growth comparable to that obtained by the use of the L isomer. The approximate supplemental requirements on this diet for orally administered L- and D-tryptophan are 0.15 and 2.1% respectively. The utilization of the D isomer as found in this study indicates a supplemental requirement for the DL mixture of approximately 0.28% of the diet.

Chicks approximately 17 days of age receiving a tryptophan-deficient diet were provided with L- or D-tryptophan by means of subcutaneous injections. Growth and an increase in nitrogen retention resulted when either isomer was given. The approximate requirements for L- and D-tryptophan when administered in this way are 91 and 236 mg/chick/day respectively. This work shows that the chick can utilize the D isomer without the assistance of the microflora and suggests that inefficient absorption is the cause of the very high requirement for orally administered D-tryptophan.

1 The data reported in this paper are taken from a thesis submitted to the Graduate College of the University of Illinois by the senior author in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Animal Nutrition.

Manuscript received 31 March 1956.




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