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Antimicrobial Growth Promotants

The use of subtherapeutic doses of antibiotics as growth promotants was yet another unintentional discovery.  In 1948, animal nutritionist Robert Stokstad and biochemist Thomas Jukes of the Lederle company, were then extensively working on a variety of vitamin B12 which was believed to be the “animal protein factor” that can enhance the growth of chickens.  Because the Lederle laboratories (the laboratory where the very first tetracycline, chlortetracycline, was discovered) uses vats of Streptomyces auerofaciens for the production of the antibiotic aureomycin, they utilized its cellular remains after the antibiotic had been extracted because they found that this contain substantial amounts of Vit B12.  They found that chicks receiving supplements of Streptomyces auerofaciens fermentation grow 24% more rapidly than those receiving liver extract, another source of this vitamin.  They later realized that this observed growth enhancement was not because of the vitamin, but due to the minimal residues of antibiotics left in the bacterial carcasses.  This opened a whole new market for antibiotics to the multi-billion dollar industry that it is today; a surprising offshoot from the vitamin research that had no direct investment return to the laboratory.