The Open Food Science Journal
2008, 2 : 38-42Published online 2008 May 6. DOI: 10.2174/1874256400802010038
Publisher ID: TOFSJ-2-38
Nonproteic Contents Interfere with the Analysis of Added Tryptophan in Feeds – Test of a Correction Model
Evonik Degussa GmbH, Feed Additives, Animal Nutrition Services, Bldg. 913-205, P.O. Box 1345, 63403 Hanau, Germany.
ABSTRACT
The nonproteic, free tryptophan contents in 23 important feed ingredients were analysed. Wheat, its bran and middlings, soybean meal, sunflower meal and other vegetable feed ingredients contain significant fractions of free tryptophan, up to 38% of total tryptophan. These natural contents considerably interfere with the accurate determination of supplemented L-tryptophan in mixed feeds. Two correction methods were successfully tested in four feeds, which were each supplemented at two levels. They allow a distinct improvement in the analysis of tryptophan addition.