Manage corn silage harvest for high-quality cattle feed
Proper harvest management is critical for high-quality corn silage, which increases milk production in cows. It all starts with harvest timing.
Silage that is too wet when harvested may not ferment properly and can lose nutrients through seepage. If silage is too dry, it has lower digestibility because of harder kernels and more lignified stover. In addition, dry silage does not pack as well, increasing the potential for air pockets and mold.
Due to variability among hybrids and fields, measure silage moisture using a commercial forage moisture tester or microwave oven rather than estimating it from the kernel starch line. Instead, the kernel starch line should be an indicator of when to collect the first silage samples for moisture testing.
A general guideline is to begin moisture testing when the starch line is 25 percent of the way down the kernel for horizontal silos, and 40 percent of the way down the kernel for vertical silos. Then, assume a constant dry-down rate of about 0.4 to 0.6 percent per day, and measure moisture again prior to harvest.
Length of cut and crop processing are also important for obtaining high-quality corn silage. This is because breakage of cobs and kernels increases surface area, which improves digestibility, reduces cob sorting by cows, and results in higher density silage that packs better. If two or more half or full kernels are present in a 32-ounce cup of silage, then more kernel breakage is needed.
Although crop processors are expensive, the higher quality of silage that they produce can increase milk production by 300 pounds per cow per year. The benefit to crop processors is greatest when there are harder kernels resulting from late harvest or drought.
When using a crop processor, chopper cut length should be increased to maintain optimum particle size for cud chewing. Ideal chop length is 3/8 inch for unprocessed corn. For processed corn, the recommended setting is 3/8 inch with .08- to .12-inch roll clearance.
When harvest begins, fill silos rapidly to reduce exposure of silage to oxygen and fungal growth. For bunker silos, pack silage as tightly as possible in progressive wedges in depths of 6 inches or less, allowing about five minutes of packing time per ton of silage.
Extra time spent to thoroughly cover bunker silos and obtain a good seal around bunker sidewalls is a good investment.
Jeff Coulter is a corn agronomist with University of Minnesota Extension.