EFFECTS OF HYBRID AND ENSILING WITH AND WITHOUT A MICROBIAL INOCULANT ON THE NUTRITIONAL CHARACTERISTICS OF WHOLE-PLANT CORN

Two corn hybrids (Pioneer 3377 and 3389) with similar total plant and grain yield characteristics were evaluated to determine potential differences in nutritive value of the whole plant and stover. Hybrids were grown in plots at four different locations in Idaho in 1988 and 1989 for laboratory evaluation. Samples from the plots were stored fresh or ensiled with or without a microbial inoculant for 60 d in laboratory silos. Whole-plant samples of 3377 had a lower (P < .01) percentage of NDF (42.7 vs 48.1), ADF (26.3 vs 30), hemicellulose (16.2 vs 18.2), cellulose (21.4 vs 24), and lignin (3.4 vs 3.8). Similar differences, but of larger magnitude, were observed in stover samples. Ruminal in situ (24 h) and two-stage IVDMD of whole-plant and stover samples were greater (P < .01) for 3377 than for 3389. Lower fiber content and greater degradability for 3377 was not due to greater grain content; 3377 actually had numerically lower grain as a percentage of whole plant than 3389 (41 vs 44). Ensiling reduced (P < .05) NDF, hemicellulose, and cellulose content compared with fresh samples; however, no effect (P > .10) due to inoculant was noted. Hybrid x storage interactions were not observed (P > .10). Inoculation and hybrid did not affect ( P > .10) organic acid concentration of the silages. In 1989 silages from 3377 and 3389 were harvested to evaluate diets containing 65% (DM basis) corn silage in steer digestion and growth trials. Digestible energy and digestibility of DM and CP were greater (P < .05), and the trend (P > .05) was for greater NDF and ADF digestibility for the 3377 than for the 3389 diet. In a growth trial, steers fed the 3377 silage diet had greater (P < .05) daily gain (1.09 vs 1.01 kg/d), consumed numerically less (P = .09) DM, and had improved (P < .01) feed efficiency (6.75 vs 7.49 feed:gain) compared with steers fed the 3389 silage diet. Results of the experiments indicate that large differences in feed value of corn silage may exist among hybrids with similar grain content.