Abstract
The subject of this assessment was the L-threonine produced by a genetically modified strain of Escherichia coli. L-Threonine is an essential amino acid for all animal species. It is widely used in the feed industry to optimise dietary protein intake. The amino acid L-threonine itself is considered safe for target animals, consumers and the environment. However, the recipient strain and its genetic modification, including the presence or absence of an antibiotic resistance gene in the product under assessment, are insufficiently characterised. Consequently, the Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) cannot make a conclusion on the safety of the product L-threonine produced by fermentation with this recombinant strain of E. coli for target animals, consumers, users and the environment. Regardless of the assessment of the genetic modification, the FEEDAP Panel has concerns regarding the safety of the simultaneous oral administration of L-threonine via water for drinking and feed. There are no concerns for users in respect of irritation to skin or eyes. In the absence of any data on sensitisation, it must be concluded that the product may have the potential to be a dermal sensitiser and should be handled accordingly. The level of endotoxins present in the product and its dusting potential indicate an inhalation risk for the user. The product is considered an efficacious source of the amino acid L-threonine for all animal species. For the supplemental L threonine to be as efficacious in ruminants as in non-ruminant species, it must be protected against degradation in the rumen.