In 1951, the U.S. Food and Drug Administration (FDA) approved the use of antibiotics on animals. In 1943, farmers in the U.S. found that pigs fed with penicillin-fermented mixture grew faster and In 1946, P. R. Moore found that low dose of streptomycin stimulated chick’s growth (Moore and Evenson, 1946; Dibner and Richards, 2005).

Subsequently, chlortetracycline, doxycycline, and sulfonamides helped growth promotion in calves, pigs, and chicken. Cunha from University of Florida and Stokstad from University of Washington reported that penicillin in fermentation mixture functioned as a growth promoter for food-animals (Cunha et al., 1951).