A common practice in confined livestock operations, is to feed low levels of antibiotics to improve rate of gain and to keep them healthy. Recently, the World Health Organization has called for farmers to stop this practice because of the possible link to an increase in antibiotic resistant organisms that can make treatment for many human diseases more difficult.
WHO contends that in some countries, about 80% of the total consumption of medically important antibiotics are used for growth promotion in healthy animals. However, the USDA responded by saying that the WHO recommendations are not in alignment with their policies, and are not based on sound science, but admitted that more data is needed to assess progress on anti-microbial use and resistance.