After 60 years of continuous use of antibiotics in pig farming, the resistance of bacteria is an issue that cannot be ignored. The way antibiotics work in relation to the improvement of pigs zootechnical parameters (average daily gain, feed conversion ratio) is not totally known.
Nevertheless, the fact that we are familiar with the intestinal bacterial flora and bacteria communities, as well as with the influence of antibiotics on them, could provide us knowledge about the use of alternative approaches regarding intestinal health. Many studies have shown modifications in bacterial populations after the use of antibiotics in the feed, which includes number of species, populations’ size and functional defects. Moreover, the genes resistant to antibiotics increased in intestinal bacterial population after they were exposed to feed antibiotics.