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Utilization of D- and L-Tryptophan by the Growing Dog^1,2,

University of Illinois, Urbana 61801

Abstract

Two 4 X 4 Latin square experiments were conducted with English Pointer puppiesto determine the growth promoting capacity of D- tryptophan (trp) relative to L-trp and to estimate the trp requirement of the growing dog. Based upon a multiple linear regression slope-ratio technique, D-trp had an efficacy value of 35.5 ± 6.4% of the ingested trp; no measurable trp was recovered in the urine of dogs fed L-trp. The trp requirement for maximal weigt gain was at least .16% for 6-to 10-wk-old dogs, between .12 and .16% for 10- to 12-wk-old dogs and <.12% for 12- to 14-wk-old dogs. The overall requirement for the 6- to 14-wk age period was .15%. Total N, as well as urea-, in urine decreased and N retention increased with increasing levels of dietary L-trp; NH₃-N, creatinine-N and fecal-N were unaffected by treatment.

¹ Dept. of Anim. Sci.

² The authors would like to acknowledge Dr. Katherine P. Boebel for her help in developing the crystalline amino acid diet used in these experiments and Dr. J. E. Corbin for his help in management of the puppies.