Corn silage has the reputation as a reliable and economic feedstuff. Corn silage is widely used in ruminant livestock rations, particularly with cattle, but I have also seen it used with sheep as well. A good thought to keep in mind is that the quality of the corn silage you produce this fall will affect your livestock for many months in to the future. Producing high quality silage depends upon good management practices at several different steps.
Corn silage is a fermented product. To be effective that fermentation must take place in an anaerobic (no oxygen) environment. The goal in this fermentation process is to achieve a pH of less than 4.0. This can be accomplished when air is removed as quickly as possible after chopping so that high concentrations of organic acids, predominantly lactic acid, are rapidly produced. This may sound simple, but implementation depends upon good decisions, harvest preparation, and some cooperation from Mother Nature.
The first and most critical step is that corn must be chopped at the right moisture or dry matter (DM) content. If you don't get this right, nothing else will matter. A DM range of 30-38% is acceptable. Silage put into a bunker silo should be at the lower end of this range while silage put into upright silos should be at the upper end. Corn less than 27 to 30% DM does not ferment properly. It produces silage that often has high concentrations of butyric acid and can have a very low pH. This silage will have an unpleasant odor and animal DM intake will be reduced. Corn chopped at higher than 40% DM does not pack well. As a result it usually does not ferment adequately, resulting in low acid concentrations, heat damage and moldy silage. Starch digestibility is usually low, causing the silage to have less energy. Silage harvest needs to start on the wetter end of the acceptable range because corn will gain DM content or lose moisture at a rate of between 0.5 to 1.0 percentage points per day. Rapid harvest is important to ensure that corn is chopped within the acceptable moisture range.
Chop length is a consideration for silage packing, feeding and animal performance. A three-eighths inch (3/8) theoretical length of cut (TLC) is recommended for corn at 32 to 36% DM. When DM is under 32%, a three-quarters (3/4) inch TLC is recommended and when DM content is above 36%, a TLC of less than 3/8 inch is recommended. There is a reason that this is termed "theoretical". The actual cut length in the field can vary so operators should look at the actual chopped forage and make adjustments to get the correct chop length. One practice that can change these recommendations is kernel processing. Kernel processing involves fracturing the corn kernels as the corn plant is chopped. Research results have consistently shown benefits in animal performance when kernels are processed adequately. The goal is to crack 90 to 95% of the kernels and 70% of those should be fractured to smaller than one-quarter of a kernel. When kernel processing is a part of the chopping process then TLC is typically increased to three-quarters of an inch.