Effects of Feeding Insect-Protected Corn and Corn Residue to Cattle, and Evaluation of Distillers Grains Storage when Mixed with Crop Residue on Cattle Performance

One grazing and two feeding experiments were conducted to compare the feeding value of corn grain, corn silage, or corn residue from a second generation insect protected (Bt) hybrid (MON 89034) developed by Monsanto including two proteins (Cry1A.105 and Cry2Ab2) with a non-transgenic parental hybrid (PAR), and two commercially available non-transgenic reference hybrids (REF1 and REF2). Diets for all three experiments were formulated to meet NRC (1996) protein requirements. In Exp. 1, two hundred forty crossbred steer calves (290 ± 14 kg) were fed a dry rolled corn and corn silage based (65 and 15% of diet DM, respectively) finishing diet in 24 pens, with six pens per corn hybrid. Dry matter intake (P = 0.48) and ADG (P = 0.90) were similar between MON 89034, CON, REF1, and REF2 treatments. Steers fed diets containing corn and corn silage from REF1 were more efficient (P = 0.05) than steers fed REF2 and PAR treatments. Carcass characteristics (HCW, marbling score, 12 rib fat thickness, LM area, calculated USDA yield grade, and percent graded choice) did not differ (P > 0.36) with regards to diets from transgenic, parental, or reference hybrids. In Exp. 2, two hundred forty crossbred steer calves (279 ± 20 kg) were fed a corn silage based (80% of diet DM) growing diet in 20 pens with five pens per corn hybrid. Ending BW, DMI, ADG, and G:F were not different (P > 0.32) based on corn silage source. In Exp. 3, two 12.4 ha fields containing corn residue from either MON 89034 or a near isogenic, nontransgenic parental hybrid (PAR) were divided into four equal sized paddocks. Sixtyfour crossbred steer calves (249 ± 8 kg) were stratified by BW and assigned randomly to one of the eight paddocks. Protein supplement was fed at 1.14 kg/d to ensure protein intake did not limit performance. Ending BW and ADG were similar for steers grazing each hybrid (P > 0.20). Based on these results, incorporation of insect resistant genes had