ELI: http://data.europa.eu/eli/reg_impl/2023/2583/oj 1/4COMMISSION IMPLEMENTING REGUL ATION (EU) 2023/2583 
of 20 November 2023
concer ning the author isation of L-isoleucine produced by Cor ynebacter ium glutamicum KCCM 80185 
as a feed additiv e for all animal species 
(Text with EEA relevance) 
THE EUR OPEAN COMMISSION,
Havi ng regar d to the Treaty on the Functioning of the European Union,
Havi ng rega rd to Regulation (EC) No 1831/2003 of the European Parliament and of the Council of 22 Sept ember 2003 on 
additives for use in animal nutr ition (1), and in particular Article 9(2) thereof,
Whereas:
(1) Regulation (EC) No 1831/2003 provid es for the author isation of additives for use in animal nutr ition and for the 
grounds and procedures for granting such an author isation.
(2) In accordance with Article 7 of Regulation (EC) No 1831/2003, an application was submitted for the author isation 
of L-isoleucine produced by Corynebacter ium glutamicum KCCM 80185. That application was accompanied by the 
particulars and documents required under Article 7(3) of Regulation (EC) No 1831/2003.
(3) The application concer ns the author isation of L-isoleucine produced by Corynebacter ium glutamicum KCCM 80185 as 
a feed additive for use in feed and in water for drinking for all animal species, requesting that additive to be classified 
in the cate gory ‘nutr itional additives’ and in the functional group ‘amino acids, their salts and analogues’.
(4) The European Food Safety Author ity (‘the Author ity’) concluded in its opinions of 10 November 2021 (2)and of 
21 March 2023 (3)that, under the proposed conditions of use, L-isoleucine produced by Corynebacter ium glutamicum 
KCCM 80185 is safe for the target species, consumers and the environment. It also concluded that the additive is 
hazardous by inhalation for persons handling the additive. The Author ity further concluded that the additive is an 
efficacious source of the essential amino acid isoleucine for non-r uminant animals and that for the supplemental 
L-isoleucine to be fully efficacious in ruminants, it should be prote cted against degradation in the rumen. The 
Authority expressed concer ns on the simultaneous oral administration of the amino acid via water for drinking and 
feed. Howe ver, the Author ity did not propose a maximum cont ent for L-isoleucine. Thus, in the case of 
supplementation with L-isoleucine via water for drinking, it is appropr iate to alert the user to take into account the 
dietar y supply with all the essential and conditionally essential amino acids. The Author ity did not consider that 
there is a need for specifi c requirements of post-market monitori ng. It also verified the repor t on the method of 
analysis of the feed additive in feed submitted by the Reference Laborator y set up by Regulation (EC) No 1831/2003.
(5) In view of the abov e, the Commission considers that L-isoleucine produced by Corynebacter ium glutamicum KCCM 
80185 satisfies the conditions provi ded for in Article 5 of Regulation (EC) No 1831/2003. According ly, the use of 
that additive should be author ised. In addition, the Commission considers that appropr iate prot ective measures 
should be taken to prevent adverse effects on the health of the users of the additive.
(6) The measures provid ed for in this Regulation are in accordance with the opinion of the Standing Committ ee on 
Plants, Animals, Food and Feed,
(1)OJ L 268, 18.10.2003, p. 29.
(2)EFSA Jour nal 2021;19(12):6977.
(3)EFSA Jour nal 2023;21(4):7957.
Offi cial Jour nal  
of the European Union EN 
L series    
2023/2583  21.11.2023ELI: http://data.europa.eu/eli/reg_impl/2023/2583/oj 2/4HAS ADOPTED THIS REGUL ATION:
Article 1
The substance specifi ed in the Annex, belonging to the additive categor y ‘nutr itional additives ’ and to the functional group 
‘amino acids, their salts and analogues’, is author ised as an additive in animal nutr ition, subject to the conditions laid down 
in that Annex.
Article 2
This Regulation shall enter into force on the twentieth day followi ng that of its publication in the Official Journal of the 
European Union.
This Regulation shall be binding in its entirety and directly applicable in all Member States.
Done at Brussels, 20 November 2023 .
For the Commission
The President
Ursula VON DER LEYENOJ L, 21.11.2023 EN  ELI: http://data.europa.eu/eli/reg_impl/2023/2583/oj 3/4ANNEX 
Identifica -
tion 
number of 
the additiveAdditiveCompo sition, chem ical formula, descr iption, 
analytical methodSpecies or 
categor y of 
animalMaxi -
mum 
ageMini -
mum 
contentMaxi -
mum 
content
Other provisionsEnd of period of 
author isationmg/kg of complet e 
feed with 12 % 
moisture content
Categor y: nutr itional additiv es. Functional group: amino acids, their salts and analogues
3c384 L-isoleucine Additive composition
Powder with a minimum content of 
L-isoleucine of 90 % (on a dry matt er basis)
Char acter isation of the active substance
L-isoleucine produced by fermentation with 
Corynebacter ium glutamicum KCCM 80185
IUPAC name: (2S,3S)-2-amino- 
3-methyl pentanoic acid
Chemical formula: C6H13NO 2
CAS number: 73-32-5
Analytical method (1)
For the identification of L-isoleucine in the 
feed additive:
— Food Chemical Codex ‘L-isoleucine 
monograph’
For the quantification of isoleucine in the 
feed additive:
— ion-ex chang e chromat ography coupled 
with post-column derivatisation and 
optical detection (IEC- VIS/FLD) or
— ion-ex chang e chromat ography coupled 
to post-column derivatisation and 
photomet ric detection (IEC- VIS)All animal 
species- - 1. In the directions for use of the additive 
and premixture, the storage conditions, 
the stability to heat treatment and in 
water shall be indicate d.
2. The additive may be used via water for 
drinking.
3. Declaration to be made on the label of 
the additive and premixture:
— ‘The supplementation with L-isoleucine, 
in particular via water for drinking, shall 
take into account all essential and condi ­
tionally essential amino acids in order to 
avoid imbalances.’
— L-isoleucine conte nt.
4. For users of the additive and premix ­
tures, feed business operat ors shall es­
tablish operational procedures and or­
gani sational measures to address 
poten tial risks resulting from their use. 
Where those risks cannot be eliminated 
by such procedures and measures, the 
additive and premixtures shall be used 
with personal breathing prot ective 
equipment.11 December 2033OJ L, 21.11.2023 EN  ELI: http://data.europa.eu/eli/reg_impl/2023/2583/oj 4/4
For the quantification of isoleucine in 
premixtures:
— ion-ex chang e chromat ography coupled 
with post-column derivatisation and 
optical detection (IEC- VIS/FLD) or
— ion-ex chang e chromat ography coupled 
to post-column derivatisation and 
photomet ric detec tion (IEC- VIS) – Com ­
mission Regulation (EC) No 152/2009 (2)
(Annex III, F)
For the quantification of isoleucine in 
compo und feed:
— ion-ex chang e chromat ography coupled 
to post-column derivatisation and 
photomet ric detection (IEC- VIS) – Regu ­
lation (EC) No 152/2009 (Annex III, F)
For the quantification of isoleucine in water:
— ion-ex chang e chromat ography coupled 
to post-column derivatisation and 
photomet ric detection (IEC- VIS)
(1)Details of the analytical methods are available at the following address of the Reference Laborato ry: https://joint-research-c entre.ec.europa.eu/eurl-fa-eurl-f eed-additives/eurl-fa-author isation/eurl-f a-evaluation- 
repor ts_en
(2)Commission Regulation (EC) No 152/2009 of 27 Januar y 2009 laying down the methods of sampling and analysis for the official control of feed (OJ L 54, 26.2.2009, p. 1).OJ L, 21.11.2023 EN  