[1][2] Methionine, lysine, and tryptophan are commonly deficient in animal diets, so these amino acids are added to feed.
Ethylenediamine dihydroiodide (EDDI) is added to pet food and cattle feed to prevent iodine deficiency.
[5] A controversial additive is arsenic, often supplied in the form of the organoarsenic compound called roxarsone.
According to EU Regulation 1831/2003,[9] all feed additives to be placed on the market within the European Union have to undergo a thorough approval process.
[citation needed] Evaluation criteria include safety for the animals, consumers and factory workers.