Influence of Brown Midrib, Leafy, and Transgenic Hybrids on Corn Forage Production

Hybrid selection strongly influences corn (Zea mays L.) forage production. Limited forage production and quality information exists for leafy and transgenic hybrids [Bacillus thuringiensis (Bt) and herbicide resistant]. We compared dry matter (DM) yield, forage quality, and estimated milk yields of these and brown midrib hybrids with dual-purpose hybrids for 3 yr at harvest densities of 66 000 and 84 000 plants ha -1 . Transgenic hybrids had no effect on DM and milk yields, so we do not recommend Bt hybrids under conditions of low infestation of European corn borer (Ostrinia nubilalis Hubner). Leafy hybrids had similar DM and milk yields as hybrids of similar maturity. Brown midrib hybrids, which had DM yields that were about 20% less than those of hybrids of similar maturity, had 40 to 80 g kg -1 greater in vitro true digestibility (IVTD) and 70 to 200 g kg -1 greater neutral detergent fiber (NDF) digestibility. Brown midrib hybrids had the greatest or least milk yields among hybrids, depending on hybrid and year. Leafy and brown midrib hybrids mostly had low harvest index (HI) values, which had strong negative correlations with NDF in all years (-0.71, -0.44, and -0.90). Brown midrib hybrids had high NDF digestibility, which had strong positive correlations with IVTD (0.80, 0.88, and 0.86). Currently, we do not recommend brown midrib hybrids because of inconsistent milk yields and high seed costs. Development of brown midrib and leafy hybrids with greater HI values should result in excellent forage hybrids.