Antibiotics are frequently used to promote the growth and improve the health of swine. While the reason why antibiotics work as growth promoters is unknown, the leading answer is because the antibiotics alter the distribution and mix of bacteria in the intestinal tract of animals. In this project we developed a set of molecular tools to measure the mix of bacteria in the intestinal tracts of pigs and to measure the concentration of these microbes. The proposal hypothesis was that this information would provide a means to use non-antibiotic agents or practices to mimic the effects of antibiotics thus reducing producer reliance on antibiotics. In this project using this new set of molecular tools we described the major microbial components of the pig intestinal tract. Of the bacteria identified, more than half (56%) were new bacteria that have not been previously described.