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Animal health problems linked to glyphosate, GM feed

By Ken Roseboro
Published: April 30, 2015

Farmers, agriculture experts seeing negative impacts of popular herbicide and GM feed on farm animals

In October 2000, Jerry Rosman, an Iowa farmer, noticed a problem with his hogs. During breeding, the female sows exhibited all signs of pregnancy, yet when the time came to deliver nothing happened, a phenomenon called “pseudopregnancy.” Over the next year, the breeding rates in Rosman’s sow herd plummeted 80 percent. Rosman eventually traced the problem back to his feed, which was genetically modified Bt corn. Laboratory tests revealed that the corn contained high levels of Fusarium, a fungal pathogen that can produce mycotoxins, which can enter the food chain and negatively affect human and animal health.

Rosman wasn’t the only farmer with the problem. More than twenty farmers in Iowa and surrounding states reported the same breeding problems. At least five farmers switched to non-GMO corn feed and the problem disappeared.

Glyphosate seen as cause for health problems

Iowa veterinarian Art Dunham, who works with dairy and beef cows and hogs, says he has seen animal health problems from GM feed since Rosman reported his problems almost 15 years ago. Dunham believes that glyphosate, the main ingredient in Roundup herbicide, which is used extensively with GM soy, corn, and other crops, is a major culprit. “The most obvious problems with glyphosate-GMO has been with the Fusarium mycotoxins noticed at first in the early 2000s and worse in the cold damp years since,” he says.

Animal health problems related to GM feed are not limited to Iowa. In 2013, New York State farmer Jim Larson had an experience similar to Rosman’s. His Yorkshire sows abruptly lost their ability to reproduce. Again, the problem was traced to mycotoxin-tainted GM feed. He then switched to non-GMO feed. In 2011, Danish hog farmer lb Borup Pedersen observed that health problems in his pigs, including ailments such as bloat, ulcers, and diarrhea were common with his use of GM soy. He switched to non-GMO feed and saw immediate improvements in the health of his sow herd. Because of the experience of Pedersen and other Danish farmers, the Danish farm minister asked scientists at Aarhus University to investigate the possible effects of glyphosate herbicides on the health of livestock. A 2013 study published in the Journal of Environmental and Analytical Toxicology found that glyphosate is toxic to the normal metabolism of dairy cows.

Some of the negative health impacts that Dunham has seen and that he links to glyphosate include reproductive problems in hogs and beef cows, botulism in dairy cows, and bloody bowels and rickets in hogs. “It definitely increases many risks and makes it harder to have healthy animals and to stay profitable,” he says.

Dunham says glyphosate alters the microbiome, which is the mixture of bacteria in the bowels necessary for health in animals and people.

“Glyphosate is not just an herbicide,” he says. “It is a very broad spectrum antibiotic.”

Glyphosate has also been found to cause a deficiency in the nutrient manganese in plants. Dunham has seen manganese deficiencies in animals raised on feed from Roundup Ready corn and soy. He says this deficiency can lead to stillborn deaths and calf health issues in dairy cows and viral diseases in hogs, such as porcine reproductive and respiratory syndrome (PRRS) and porcine circovirus (PCV). “I have confirmed the problem of manganese deficiency in high mortality cases of PRRS and PCV in hogs,” Dunham says.

Published studies show negative impacts of glyphosate

Published research by Don Huber, emeritus professor of plant pathology from Purdue University, and Robert Kremer, microbiologist with the University of Missiouri, has found many negative impacts of glyphosate on plant health. The scientists’ research has also found that glyphosate increases populations of Fusarium.

In fact, Huber says there are more than 40 plant diseases associated with the use of glyphosate.

In a 2009 interview, Kremer said: “We’ve taken field surveys and seen an increase in Fusarium with the use of glyphosate. Some Roundup Ready varieties even without using glyphosate tend to be more susceptible to being impacted by Fusarium. It could be an unintended consequence of genetic manipulation that could make it more susceptible.”

In a 2011 presentation, Huber called glyphosate the “most abused chemical in the history of agriculture” and described GM crops as a “failed system.”

GMO-fed pigs suffered severe stomach inflammation

A 2013 study published in Journal of Organic Systems found that pigs were harmed by the consumption of feed containing GM corn and soy. GM-fed pigs suffered severe stomach inflammation that was markedly higher than in pigs fed non-GMO feed. Also, GMO-fed females had on average 25 percent heavier uteri than non-GMO-fed females, a possible indicator of disease that requires further investigation. The study’s findings were significant because they were found in actual farm conditions and not in a laboratory.

“Our results provide clear evidence that regulators need to safety assess GM crops containing mixtures of GM genes, regardless of whether those genes occur in the one GM plant or in a mixture of GM plants eaten in the same meal, even if regulators have already assessed GM plants containing single GM genes in the mixture,” said lead researcher Dr. Judy Carman, adjunct associate professor at Flinders University, Adelaide, Australia.

The cause of Jerry Rosman’s hog reproductive problems was never determined. Scientists at Iowa State University and the seed company that sold Rosman the corn claimed Bt corn was not the problem. Rosman believes some people want to see the problem disappear. “They don’t want to admit there is a problem,” says Rosman, who blocked sale of the corn, fearing it could cause harm if it entered the food supply. “If this happened here, where else could it happen?”


  • Tracy Frisch, “Why some farmers are avoiding genetically modified feed crops,” Hill Country Observer, Dec. 2013/Jan. 2014.

  • Monika Krüger, Wieland Schröd, Jürgen Neuhaus and Awad Ali Shehata, “Field Investigations of Glyphosate in Urine of Danish Dairy Cows,” Journal of Environmental and Analytical Toxicology, Volume 5, Issue 3, 2013.

  • Sebastian Bott, Tsehaye Tesfamariam, Hande Candan, Ismail Cakmak, Volker Römheld, Günter Neumann, “Glyphosate-induced impairment of plant growth and micronutrient status in glyphosate-resistant soybean,” Plant Soil, August 2008, pgs. 185-194.
  • M.R. Fernandeza, R.P. Zentner, P. Basnyat, D. Gehl, F. Selles, D. Huber, “Glyphosate associations with cereal diseases caused by Fusarium spp. in the Canadian Prairies,” European Journal of Agronomy, 31 (2009), pgs. 133-143.

  • Robert J. KremerNathan E. Means, “Glyphosate and glyphosate-resistant crop interactions with rhizosphere microorganisms,” European Journal of Agronomy, 31 (2009), pgs. 153-161.

  • Ken Roseboro, “Scientist finding many negative impacts of Roundup Ready GM crops,” The Organic & Non-GMO Report, December 2009/January 2010, pgs. 4-6.

  • Ken Roseboro, “Scientist warns of dire consequences with the widespread use of glyphosate,” The Organic & Non-GMO Report, May 2010, pgs. 4-6.

  • Ken Roseboro, “Scientist says flawed science of GMOs jeopardizing future generations,” The Organic & Non-GMO Report, March 2012, pgs. 17-18.

  • Judy A. Carman, Howard R. Vlieger, Larry J. Ver Steeg, Verlyn E. Sneller, Garth W. Robinson, Catherine A. Clinch-Jones, Julie I. Haynes, John W. Edwards, “A long-term toxicology study on pigs fed a combined genetically modified (GM) soy and GM maize diet,” Journal of Organic Systems, 8(1), 2013.

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