J. Anim Sci.
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J. Anim Sci. 1986. 62:660-664.
© 1986 American Society of Animal Science
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Tryptophan Requirement of Growing Swine as Determined by the Oxidation of an Indicator Amino Acid1,2,

F. D. Lin, T. K. Smith and H. S. Bayley

University of Guelph3 Ontario, Canada N1G 2W1

Abstract

The tryptophan requirement of growing swine was determined using the oxidation of L-[1-14C]-phenylalanine as an indicator of the adequacy of the dietary tryptophan level. Forty crossbred boars (30 to 45 kg) were fed a basal diet containing 16% protein supplied by corn and gelatin. A series of experimental diets containing .05, .08, .10, .15, .20 and .25% L-tryptophan were prepared. The diets were supplemented with crystalline amino acids to provide 135% of the recommended levels. Release of 14CO2 was measured for 1 h following a meal of the experimental diet containing 20 µCi 14C phenylalanine. Increasing dietary tryptophan from .05 to .13% decreased release of 14CO2. Further increases in dietary tryptophan concentration did not significantly influence 14CO2 production. Regression analysis using a two-phase linear regression crossover model indicated that phenylalanine oxidation was minimized by a dietary tryptophan concentration of .13%. It was concluded that at a concentration of .13%, tryptophan was no longer limiting the retention of the other amino acids, thus this is the requirement for maximum protein retention by the young, growing boar.

Footnotes

1 Supported by the Nat. Sci. and Eng. Res. Council of Canada and the Ontario Ministry of Agr. and Food.

2 The authors are grateful for the technical assistance of Mr. Donald Saunders, Mr. Ralph Robinson and Mr. Andrew Pharazyn.

3 Dept. of Nutr.






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Copyright © 1986 by the American Society of Animal Science.