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By Jacquelyn Prestegaard, ASAS Communications

Genetically engineered (GE) crops are amongst agriculture’s most disputed topics. Their use directly impacts the livestock industry as “food-producing animals consume 70 to 90% of the GE crop biomass.” Since their introduction in 1996, some 100 billion sheep, goats, pigs, chickens, quail, cattle, water buffalo, rabbits, and fish have consumed GE crops.

University of California-Davis geneticist Dr. Alison Van Eenennaam and research associate Ms. Amy E. Young analyzed GE feedstuffs in one of the most comprehensive reviews of its kind. Their paper, “Prevalence and impacts of genetically engineered feedstuffs on livestock populations,” appeared in October’s edition of the Journal of Animal Science. The paper highlights the most significant data compiled about livestock feed, both conventional and non-conventional, over the last 29 years.

“There have been a handful of sensational studies suggesting that genetically engineered feedstuffs cause health problems in livestock,” Van Eenennaam said. “In this review paper we summarize the findings of the large number of peer-reviewed articles that have documented the effects of GE feed on animal health, and also examine the health trends in the large commercial livestock populations that have been consuming GE feed for well over a decade.”

In the United States, 165 crop events in 19 plant species have been approved, particularly plants used for livestock feed. Extensive testing is required before the approval of any genetically modified crop. Internationally accepted guidelines developed by the Codex Alimentarius Commission are followed during the risk assessment of each plant.

Many long-term and short-term studies have been conducted on GE feeds, including ones extending across multiple generations. Of particular significance were comprehensive feeding studies involving an insecticidal variety of GE corn expressing the Cry1Ab protein from Bacillus thuringiensis, commonly called Bt corn.

Results from these comprehensive studies showed that GE feed had virtually the same composition and nutritional quality as its nonconventional counterpart. Additionally, no long-term adverse effects resulted from the feeding of Bt corn. Neither of the proteins unique to Bt corn was found in the blood, organs, or products of animals fed GE corn. As a result, “neither the intact rDNA nor the intact recombinant protein migrated from the digestive system of the animal into other body tissues or edible animal products.”

“Studies have repeatedly shown that the milk, meat, and eggs derived from animals that have consumed GE feed are indistinguishable from products derived from animals fed a non-GE diet,” Van Eenennaam said.

Authors hypothesize that if genetically engineered feeds had negative impacts on the animals consuming them, animal health and performance would decline as a result. To determine this, livestock production statistics were collected from a number of publicly available databases. Analysis of these data showed that animal health has actually increased since the introduction of GE feeds, with lower mortality rates in the poultry industry, lower somatic cell counts in dairy cows, and lower postmortem condemnation rates in cattle.

Another important observation in the review is the very high prevalence of GE feed globally. Countries that are cultivating large areas of GE corn and soy (Argentina, Brazil, and the United States) are the major livestock feed exporters, with the major importers being animal agriculture in the European Union and China. Since the exchange of GE feeds is so widespread, Van Eenennaam says consistent regulation standards are needed in the industry.

“Given there are a large number of GE crops modified to improve their usefulness as livestock feed in the regulatory pipeline, there is a pressing need for international harmonization of regulations to prevent widespread disruptions in international trade of livestock feedstuffs in the future,” she said. “This has already resulted in trade disruptions between countries that are cultivating GE crops and major import markets.”

Read an ASAS press release about this article.


Media Contact:
Jacquelyn Prestegaard

ASAS Communications



Scientific Contact:
Larry Reynolds
ASAS Media Communications