MSUToday
Published: Jan. 16, 2012

Study provides new insights into antibiotics and pig feeds

Contact(s): Layne Cameron Media Communications office: (517) 353-8819 cell: (765) 748-4827 Layne.Cameron@cabs.msu.edu, Thad Stanton USDA-ARS National Animal Disease Center office: (515) 337-7244 thad.stanton@ars.usda.gov, James Tiedje Plant, Soil and Microbial Sciences office: (517) 355-0271, ext. 1287 cell: (517) 974-5397 tiedjej@msu.edu

EAST LANSING, Mich. — Antibiotics in pig feed increased the number of antibiotic resistant genes in gastrointestinal microbes in pigs, according to a study conducted by Michigan State University and the U.S. Department of Agriculture’s Agricultural Research Service.

Published in the current edition of the Proceedings of the National Academy of Sciences, the comprehensive study focused on understanding the effects of conventional, in-feed antibiotics in U.S. farms.

For decades, many producers of pigs, chickens and other farm animals have used antibiotics not only to protect their livestock from disease, but also to boost growth rates and enhance feed efficiency, a measure of how well animals convert feed into weight gains.

Scientists don’t know precisely how antibiotics enhance growth rates and feed efficiency, but they are concerned that on-farm use of these medications may contribute to the development of strains of microbes resistant to conventional antibiotics, which are potentially harmful to humans and animals, said James Tiedje, MSU University Distinguished Professor of microbiology and molecular genetics and of crop and soil sciences.

“The growth of antibiotic resistance in pathogens is a huge challenge for society around the world,” said Tiedje, an MSU AgBioResearch scientist. “Studies to understand what contributes to the spread and what interventions can help control the problem are vital.”

Additional findings include:

  • Both diversity and abundance of antibiotic resistance genes increased in the intestinal microbial communities of the pigs treated with antibiotics. Longer term studies are needed.
  • Some of the genes found in the treated pigs were unexpected and usually linked to antibiotics not used in the study.
  • Microbial genes associated with production and use of energy by microbes increased in abundance in the antibiotic-fed pigs, which may shed light on how antibiotics increase livestock growth and feed efficiency.
  • E. coli populations increased in the intestines of the treated pigs. Further study is needed to clarify this observation.

“To our knowledge, this study is the first of its kind to look at the collateral impacts of in-feed antibiotic use in farm animals, using a comprehensive approach to detect shifts in the function and the makeup or membership of the microbial community in the model animal’s gastrointestinal tract,” said Torey Looft, USDA researcher.

Additional MSU researchers included Tim Johnson, doctoral student; Robert Stedtfeld, civil and environmental engineering research associate; Woo Jun Sul, doctoral student; Tiffany Stedtfeld, civil and environmental engineering technical aide; Benli Chai, information technologist, Center for Microbial Ecology; James Cole, assistant professor at the Center for Microbial Ecology; and Syed Hashsham, civil and environmental engineering professor.

Funding was provided by MSU’s Environmental Science and Policy Program initiative on Pharmaceuticals in the Environment, ARS and the National Institutes of Health and through the Alliance for the Prudent Use of Antibiotics program on Reservoirs of Antibiotic Resistance.

###

Michigan State University has been working to advance the common good in uncommon ways for more than 150 years. One of the top research universities in the world, MSU focuses its vast resources on creating solutions to some of the world’s most pressing challenges, while providing life-changing opportunities to a diverse and inclusive academic community through more than 200 programs of study in 17 degree-granting colleges.

As the USDA’s chief scientific research agency, ARS is leading America toward a better future through agricultural research and information. ARS conducts research to develop and transfer solutions to help answer agricultural questions that impact Americans every day.