Details Publication date8 August 2025 (Last updated on: 27 August 2025)AuthorJoint Research Centre Description In the current application an authorisation is sought under Article 4 for L isoleucine produced by fermentation with Escherichia coli CCTCC M 20231916, under the category/functional group 3(c) 'nutritional additives'/'amino acids, their salts and analogues', according to Annex I of Regulation (EC) No 1831/2003. The authorisation is sought for all animal species. According to the Applicant, the feed additive contains L-isoleucine as an active substance with a minimum purity of 90 % (w/w, based on dry matter). The feed additive is intended to be added directly to compound feed or through premixtures (or complementary feed) and water. However, the Applicant did not propose a minimum or maximum L-isoleucine content in compound feed or water.For the determination of isoleucine in the feed additive and premixtures the Applicant proposed the EN ISO 17180 method based on ion-exchange chromatography (IEC) with optical (visible - VIS or fluorescence - FLD) detection.The EURL is aware on the suitability of the above-mentioned method for the determination of other various amino acids (isoleucine included) in feed additives and premixtures and considers it applicable for the current product.For the determination of isoleucine in compound feed and water the Applicant proposed the ring-trial validated European Union (EU) method (Commission Regulation (EC) No 152/2009) based on IEC-VIS, which is equivalent to EN ISO 13903 method and provided experimental evidences demonstrating the applicability of the above-mentioned EU method for the determination of isoleucine in the feed additive, premixtures and water.In addition, the EURL is aware of the Food Chemical Codex (FCC) L-isoleucine monograph and considers it applicable for the identification of L-isoleucine in the current product.Based on the performance characteristics and available data the EURL recommends for official control: (i) the Food Chemical Codex (FCC) “L-isoleucine monograph” for the identification of L-isoleucine in the feed additive (ii) the EN ISO 17180 based on ion-exchange chromatography coupled to optical detection (IEC-VIS/FLD) to determine isoleucine in the feed additive and premixtures; and (iii) the European Union (EU) method (or equivalent EN ISO 13903 method) based on ion-exchange chromatography coupled to optical detection (IEC-VIS) for the determination of isoleucine in the feed additive, premixtures compound feed and water.Further testing or validation of the methods to be performed through the consortium of National Reference Laboratories as specified by Article 10 (Commission Regulation (EC) No 378/2005, as last amended by Regulation (EU) 2015/1761) is not considered necessary. Files 8 AUGUST 2025finrep-feed-2024-28079-isoleucine.pdf