Why have antibiotics been added to pig diets?
The initial use of antibiotics in diets arose from the discovery in the late 1940’s, in the United States, that including the fermentation products of Streptomyces aureofaciens (a strain of bacteria) in the diets of simple-stomached animals, such as pigs and poultry, resulted in growth responses. In the next fifty years, the use of antibiotics as feed additives in pig and poultry production became virtually universal. How do feed antibiotics promote growth in pigs and poultry? The exact mechanism as to how feed antibiotics ‘promote’ growth is not entirely clear. It is probable that they allow animals to express their natural potential for growth, and that the ‘growth promotion’ is achieved by antibiotics exerting their effects through a direct influence on bacteria in the animal gut, since there is no response in germ-free animals. Antibiotics used as routine feed additives also appear to prevent some diseases, since their withdrawal can result in the emergence of endemic conditions pa
