l-Threonine, technically pure, is a feed additive produced by fermentation using a genetically modified (GM) strain of Escherichia coli (CGMCC 7.58). The Panel on Additives and Products or Substances used in Animal Feed (FEEDAP Panel) of EFSA issued an opinion on the safety and efficacy of the product, which concluded that 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 FEEDAP Panel could not 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. Furthermore, the level of endotoxins present in the product and its dusting potential represent a risk for the user by inhalation. The European Commission asked EFSA to deliver an opinion on the safety of l-threonine for all animal species based on additional data submitted by the applicant on the characterisation of the additive and of the genetic modification of the production strain. No recombinant antibiotic resistance genes are present in the production strain and therefore in the final product. l-Threonine technically pure, manufactured by fermentation using E. coli CGMCC 7.58, does not raise safety concerns for the target species, consumers, users and the environment with regard to the genetic modification of the production strain. A risk from exposure to endotoxins for people handling the additive is expected. Concerns remain about possible dermal sensitisation.