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Research has been conducted on genetically modified corn fed to livestock since the introduction of insect resistant hybrids. While the overwhelming conclusion of these trials demonstrate nutritional equivalency to corn from non-transgenic hybrids, the introduction of new transgenes and combinations of resistance traits necessitates continued evaluation of genetically modified corn hybrids. Expansion of the ethanol industry has resulted in the increased availability of co-products for use as a livestock feed, as well as an increase in crop residues that offer unique opportunities for use by cattle producers. A finishing trial was conducted with corn and corn silage from MON 89034, which incorporates two genes encoding for insect resistance. The presence of the transgenes in MON 89034 did not impact finishing performance or carcass characteristics when compared to steers fed corn and corn silage from a near isogenic, non-transgenic parental hybrid and two non-transgenic reference hybrids. Growing steers were fed silage from corn hybrid MON 89034 and performance was compared to that of steers fed silage from the isogenic, non-transgenic parental hybrid and two non-transgenic reference hybrids. No differences in performance were observed. A grazing trial evaluated the performance of steers grazing corn residue from hybrid MON 89034 and its isogenic, non-transgenic parental hybrids, and no differences in performance were observed. An individual trial was conducted to determine the effects of ensiled (EN) or freshly mixed (FR) modified distillers grains with solubles (MDGS) blended with corn stalks (CS) or wheat straw (WS) at 30% or 50% diet DM. Steers offered EN blends had greater DMI, ADG, and G:F than steers fed FR blends. Growing steers were offered the same MDGS:crop residue blends as those in the individual trial, but as a supplement to a basal forage diet to determine palatability and forage intake replacement. Steers offered all mixes equaled or surpassed ADG and G:F of steers offered only the basal forage diet, with blends replacing 9.6% to 35.4% of the basal diet.
Advisors: Galen E. Erickson and Terry J. Klopfenstein