RESEARCH ARTICLE


Nonproteic Contents Interfere with the Analysis of Added Tryptophan in Feeds – Test of a Correction Model



Johannes Fontaine*, Elke Berlemann, Wolfgang Polzer
Evonik Degussa GmbH, Feed Additives, Animal Nutrition Services, Bldg. 913-205, P.O. Box 1345, 63403 Hanau, Germany.


© 2008 Fontaine et al.;

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: https://creativecommons.org/licenses/by/4.0/legalcode. This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Evonik Degussa GmbH, Feed Additives, Animal Nutrition Services, Bldg. 913-205, P.O. Box 1345, 63403 Hanau, Germany; E-mail: johannes.fontaine@evonik.com


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.

Keywords: Free, nonproteic Tryptophan, amino acid analysis, supplementation, blank value, mixed feed, feed ingredients, raw materials, wheat, wheat bran.