Update on Corn Silage Harvesting Practices

Dr. Bill Weiss, Dairy Specialist, Ohio State University

As corn silage harvest approaches, important decisions must be made regarding silage harvest. The quality of the silage made this fall will have an impact on the herd for the next 12 months.

When to chop. The decision to chop should be based on the dry matter (DM) concentration of the corn plants. Corn silage that is excessively wet can reduce intake when fed to dairy cows and can produce effluent (seepage) during storage. Silage that is too dry has poorer digestibility and can heat in the silo and feed bunk. The ideal DM concentration for corn silage is between 30 and 38% (bunkers should be at the low end of this range, bags in the mid portion of the range, and upright silos at the upper end of this range). Although kernel milk line is related with DM concentration of corn plants, milk line is not accurate enough to make harvesting decisions. Based on a study from Ohio, average DM concentration of corn plants was 35% (range was approximately 30 to 40%) at one-quarter milk line (milkline one-fourth of the way down from the tip to the base of the kernel) and 39% (range was approximately 35 to 45%) at one-half milk line stage. Planting time and hybrid affected the relationship between milk line stage and DM concentration. A sample of corn plants from the field should be chopped and analyzed for DM using either a microwave or Koster tester before filling the silo. Monitoring DM should begin at the full dent stage.

Kernel Processing. Kernel processing allows corn silage to be chopped coarsely without decreasing digestibility of the kernel (i.e., starch). The goal of processing is to damage or break most (more than 90%) of the kernels. If more than a few whole kernels are found after chopping, the processing rolls were not set close enough. Most studies have reported increased starch digestibility by dairy cows when fed kernel processed corn silage; however, digestibility of DM (an estimate of the energy value of the diet) is often not affected by kernel processing. Likewise, averaged across studies, milk production is not greatly increased by kernel processing, but some individual studies have reported large increases in milk production. Hybrid appears to be one factor affecting the response to kernel processing. Unfortunately, at this time, we do not know which hybrids are likely to respond to kernel processing.

Inoculation. Conventional corn silage inoculants provide specific lactic acid producing bacteria. Inoculated corn silage usually has a higher lactic acid concentration and lower fermentation losses than uninoculated corn silage. Milk production is seldom affected greatly by corn silage inoculation. On average, the use of lactic acid producing inoculants on corn silage probably has a slightly positive return on investment. A newer type of inoculant (Lactobacillus buchneri) promotes increased acetic acid concentrations in silage. Acetic acid is inhibitory to many yeasts and mold, and silage inoculated with L. buchneri is much more stable when exposed to air than untreated silage. This should reduce storage losses and prolong bunk-life of TMR containing inoculated silage. Limited research has found no effects on intake or milk production when cows were fed corn silage inoculated with L. buchneri. If silage feed out rate will be slow (less than about 6 inches/day) and/or the silage will be fed in the summer, L. buchneri could be quite useful.