Estimates of Corn Residue Quality

Two experiments were conducted to evaluate the effects of corn residue harvest method on animal performance and diet digestibility. Experiment 1 was designed as a 2 x 2 + 1 factorial arrangement of treatments using 60 individually fed crossbred steers (initial BW = 283; SD = 32 kg; n = 12). Factors were corn residue harvest method (highstem and conventional) and supplemental RUP at 2 concentrations (0 and 3.3% diet DM). A third harvest method (low-stem) was also evaluated with the inclusion of supplemental RUP at 3.3% diet DM. In Exp. 2, nine crossbred wethers were blocked by BW (initial BW = 42.4; SD = 7 kg) and randomly assigned to diets containing corn residue harvested 1 of 3 ways (low-stem, high-stem, and conventional). In Exp. 1, steers fed the low-stem residue diet had greater ADG compared to the conventionally harvested corn residue (P < 0.05), whereas high-stem was intermediate (0.78, 0.69, 0.63 ± 0.07 for low-stem, highstem, and conventional, respectively). Results from in vitro OM digestibility suggest low-stem residue had greatest amount of digestible organic matter compared to the other two residue methods, which did not differ (55.0, 47.8, 47.1% for low-stem, high-stem, and conventional, respectively; P < 0.05). There were no differences in RUP content (40% of CP) and RUP digestibility (60%) among the three residues (P ≥ 0.35). No interactions were observed between harvest method and addition of RUP (P ≥ 0.12). The addition of RUP resulted in an improvement in ADG (0.66, 0.58 ± 0.06 for supplemental RUP and no RUP, respectively; P = 0.08), and G: F (0.116, 0.095 ± 0.020 for supplemental RUP and no RUP, respectively; P = 0.02) compared to the same diets without the additional RUP. In Exp. 2, low-stem had greater DM and OM digestibility 54 and digestible energy (P < 0.01) than high-stem and conventional which did not differ (P ≥ 0.63). Low-stem also had greatest NDF digestibility (NDFD, P < 0.01), while highstem had greater NDFD than conventional (P < 0.01). Digestible energy was greatest for low stem (P < 0.05) and did not differ between high-stem and conventional (P = 0.50). Reducing the proportion of stem in the bale through changes in the harvest method increased the quality of corn residue.