Feeding or grazing genetically modified (GM) corn doesn't affect animal performance. The University of Nebraska (NU) study, which involved Bt corn for rootworms and Roundup Ready corn, reinforced earlier findings of the feed value of GM crops by scientists at other land-grant universities, says NU animal scientist Galen Erickson.

NU animal scientists have evaluated performance of livestock fed or grazed on GM corn for the last three years to provide information on these new types of corn, Erickson says. It's pertinent because 60% of the U.S. corn supply is fed to livestock.

“It's important that if we change corn traits that we do not decrease the feeding value,” Erickson says. “Bt and Roundup Ready corn are very advantageous from an agronomic point, but we needed to research this to ensure that the feed value was not negatively impacted.”

In two finishing trials, 200 steers were fed rations containing either Roundup Ready corn or a conventional but genetically similar hybrid, and 200 crossbred yearling steers received Bt corn for rootworms or genetically similar conventional corn. Animal performance and carcass data for these trials showed no significant differences.

Erickson says producers sometimes report that cattle spend more time grazing conventional cornstalks than Bt cornstalks. However, Erickson says this apparent preference probably is because there's more corn left after harvest in conventional cornfields with insect damage.