Tryptophan requirement of the 2.5-kg piglet determined by the oxidation of an indicator amino acid.
The tryptophan requirement of 2.5-kg piglets was measured by the oxidation of L-[1-14C]phenylalanine or DL-[1-14C]lysine when meals containing various levels of L-tryptophan were offered. Increasing dietary tryptophan from 0.65 to 2.0 g/kg decreased 14CO2 release from L-[1-14C]phenylalanine but further increases in dietary tryptophan level resulted in no further decrease in 14CO2 output. Regression analysis, with a crossover model, showed phenylalanine oxidation was minimized with a dietary tryptophan level of 1.94 g/kg (95% confidence limits 1.93 to 1.95). The oxidation of lysine was also reduced by increasing tryptophan levels to 2 g/kg; as tryptophan level was increased to 3 g/kg there was no statistically significant reduction of lysine oxidation. These studies suggest that the dietary tryptophan requirement of the 2.5-kg piglet is no more than 2 g/kg of a 240 g protein per kilogram diet.
D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D001835:Body Weight; D001944:Breath Tests; D004032:Diet; D008239:Lysine / Q000378:metabolism; D008297:Male; D009751:Nutritional Requirements; D010084:Oxidation-Reduction; D010649:Phenylalanine / Q000378:metabolism; D013552:Swine / Q000378:metabolism*; D014364:Tryptophan / Q000008:administration & dosage*
D000596:Amino Acids; D010649:Phenylalanine; D014364:Tryptophan; D008239:Lysine