‘…But I would like to sound one note of warning. Penicil-lin is to all intents and purposes non-poisonous so thereis no need to worry about giving an overdose and poi-soning the patient. There may be a danger, though, inunderdosage. It is not difficult to make microbes resis-tant to penicillin in the laboratory by exposing them toconcentrations not sufficient to kill them, and the samething has occasionally happened in the body. The timemay come when penicillin can be bought by anyone inthe shops. Then there is the danger that the ignorantman may easily underdose himself and by exposing hismicrobes to non-lethal quantities of the drug make themresistant…’- Alexander Fleming in his Nobel acceptancespeech, 1945In 2018, global meat production reached 342 milliontons, which corresponds to an increase of 47% comparedto 2000. The growing demand for animal protein makesthe livestock sector the largest user of land resourcesand the demand is expected to more than double by2030 (Robinson and Pozzi, 2011). Since the 1940s, live-stock feed has been supplemented with non-therapeuticdoses of antibiotics as they were found to improve meatproduction through increased feed conversion.