YIELD, CHEMICAL-COMPOSITION, AND RUMINAL FERMENTABILITY OF CORN WHOLE PLANT, EAR, AND STOVER AS AFFECTED BY HYBRID

Total dry matter (DM) yield and grain content are commonly considered the most important factors for evaluating corn (Zea mays L.) hybrids for silage production with no consideration given to the nutritive value of the nongrain portion of the plant. Because the nongrain portion may represent over 50% of the total DM in corn silage, we hypothesized that hybrid differences in chemical composition and ruminal fermentability of the stover portion of the plant may account for important nutritional differences in corn hybrids. Six corn hybrids were planted at two locations (Nampa, ID, and Modesto, CA) and were harvested at three stages of plant maturity. Differences (P < 0.01) in content of fiber components in whole plant and stover were observed among hybrids. Ranges in hybrid means for whole plant and stover samples were: neutral detergent fiber (NDF), 41.7 to 49.0 and 50.3 to 64.1%; acid detergent fiber (ADF), 23.9 to 28.3 and 31.7 to 41.0%; cellulose, 19.2 to 22.6 and 25.5 to 33.1%; and lignin, 2.6 to 3.3 and 3.1 to 4.4%, respectively. Hybrid composition differences in total sugar and starch of stover and total sugar of whole plant also were observed. In situ DM degradability after 24 h of ruminal incubation ranged among hybrids from 53.7 to 60.6% for whole-plant samples and from 44.0 to 52.3% for stover samples. Importantly, those hybrids with lower fiber content or higher in situ fermentability did not necessarily have greater proportion of grain in the whole plant, suggesting that selection of high quality silage hybrids may be accomplished by selecting for both high stover digestibility and high grain yields. Correlation coefficients for whole-plant in situ DM degradability with neutral detergent fiber, acid detergent fiber, cellulose, lignin, and starch were -0.85, -0.80, -0.79, -0.58, and 0.69, respectively. Results of this study indicate that differences among corn hybrids in whole-plant and stover fiber content may be important in identification of hybrids with improved silage feeding value.