The discovery of antimicrobials is one of the most significant achievements of modern medicine and has substantially contributed to a reduction in the burden of common infectious diseases of humans and livestock globally. The term "antibiotic growth promoter" is used to describe any medicine that destroys or inhibits bacteria and is administered at a low, sub therapeutic dose. According to the National Office of Animal Health (NOAH, 2001), antibiotic growth promoters are used to "help growing animals. digest their food more efficiently, get maximum benefit from it and allow them to develop into strong and healthy individuals. The use of antibiotics for growth promotion has arisen with the intensification of livestock farming. Infectious agents reduce the yield of farmed food animals and, to control these, continous administration of sub-therapeutic antibiotics and antimicrobial agents has been shown to be effective. However, the widespread use of antimicrobials in hu...