The study adds to an intensifying public debate over the impact of genetically modified crops, which are widely used by U.S. and Latin American farmers and in many other countries around the world.
The study was published in the June issue of the peer-reviewed Journal of Organic Systems by researchers from Australia who worked with two veterinarians and a farmer in Iowa to study the U.S. pigs.
Lead researcher Judy Carman is an epidemiologist and biochemist and director of the Institute of Health and Environmental Research in Adelaide, Australia.
The study was conducted over 22.7 weeks using 168 newly weaned pigs in a commercial U.S. piggery.
One group of 84 ate a diet that incorporated genetically modified (GM) soy and corn, and the other group of 84 pigs ate an equivalent non-GM diet. The corn and soy feed was obtained from commercial suppliers, the study said, and the pigs were reared under identical housing and feeding conditions. The pigs were then slaughtered roughly five months later and autopsied by veterinarians who were not informed which pigs were fed on the GM diet and which were from the control group.
Researchers said there were no differences seen between pigs fed the GM and non-GM diets for feed intake, weight gain, mortality, and routine blood biochemistry measurements.
But those pigs that ate the GM diet had a higher rate of severe stomach inflammation - 32 percent of GM-fed pigs compared to 12 percent of non-GM-fed pigs. The inflammation was worse in GM-fed males compared to non-GM fed males by a factor of 4.0, and GM-fed females compared to non-GM-fed females by a factor of 2.2. As well, GM-fed pigs had uteri that were 25 percent heavier than non-GM fed pigs, the study said.