Utilization of Bt Corn For Beef Cattle

Harvesting corn silage in Pennsylvania

Mark Antle
Department of Crop and Soil Sciences
Penn State
January 2000

Now that the use of Bt corn hybrids is increasing nationwide, many questions have been posed by beef producers regarding the performance of beef animals when fed diets consisting of Bt corn. In response to some of these concerns, two trials were performed by the University of Nebraska in cooperation with Novartis Seeds. The researchers, J. D. Folmer, G. E. Erickson, C.T. Milton, T.J.Klopfstein, and J.F. Beck, wanted to determine if any animal performance differences existed between two corn varieties, (N7333 and N4242) and their Bt counterparts. They also wanted to determine whether a variety difference played a role in animal performance.

The first trial utilized fields of N7333 Bt and N7333 non-Bt post-harvest corn residue to evaluate daily gain and grazing preference. Twenty-three acres of Bt and 21 acres of non-Bt corn fields were each divided into 3 pastures and stocked with 8 or 9 steers per pasture in order to provide equal stocking rates. Over a 70 day grazing period, daily gains of the steers were similar (.62 lb. per day) between the Bt and non-Bt pastures. Grazing preference was evaluated by allowing 16 steers equal access to 7 acres of Bt or non-Bt corn residue. The steers showed no preference for either the Bt or non-Bt fields. It should be pointed out that there was very little corn borer pressure in either the Bt or non-Bt fields. The published results of the trial did not provide information on stalk quality, but it could be surmised that quality was similar for both types of corn residue.

In the second trial, 128 steers (average weight 620 lb.) were fed either Bt or non-Bt corn silage from either N7333 or N4242 for 101 days. Dry matter intake averaged higher for steers fed Bt corn silage for both varieties. Daily gain was significantly higher for cattle fed N4242 Bt ( 3.3 lbs/day) compared to N4242 non-Bt (3.0 lbs/day), but was similar for N7333 Bt compared to N7333 non-Bt (2.9 lbs/day). Feed efficiency was significantly higher for animals fed N7333 non-Bt compared to N7333 Bt, but similar for N4242 Bt vs. N4242 non-Bt. When comparing across the two varieties, overall the steers gained 11% faster and 8% more efficiently on N4242 compared to N7333.

Based on the results of the trial performed at the University of Nebraska, it appears that the presence of the Bt trait in corn hybrids does not have a consistent affect on performance of growing steers. The study does support the popular notion that hybrid genotype plays an important role in animal performance.