To ensure good storage and fermentation, Karla Hernandez, SDSU Extension Forages Field Specialist said that corn for silage should typically be harvested between 60-70 moisture. "One of the main characteristics of corn silage is that it is well-suited to preserve forage at an optimum harvest stage that maximizes energy content," Hernandez said.
The key to good fermentation is adequate moisture content. "It results in a rapid pH drop to near 4.0, which is characteristic of well-preserved corn silage," she said. "Growers need to pay attention to maturity stage, and leaf/stem ratio. Shrink losses are usually minimized by chopping fine enough, filling rapidly, packing, and an adequate and fast sealing with an air-tight cover."
A very basic estimate of whole plant moisture for harvest can be made using the kernel milk line. The kernel milk line is the dividing line between sugars in the maturing kernel and starch deposited. "Most producers in South Dakota will use the one-third milk line as the point to start checking whole plant moisture to determine the optimum timing for silage harvest," Hernandez said.
On the other hand, maximizing the nutritional quality of corn silage and minimizing shrink losses are two main factors to take into consideration when feeding livestock.
"Therefore, harvesting corn silage too early at less than 30 percent dry matter (DM) will result in lower starch concentration in the silage," she said. "However, mature corn silage – silage with more than 38 percent DM – could also have less nutritional value because of lower fiber and starch digestibility."
Factors affecting shrink losses
Some of the factors that affect shrink losses are the following:
- Type of structure: bunkers usually have the greatest shrink when compared to other types of storage structures.
- Chop length: finely chopped forages are better and lead to increase silage density. Overall, corn silage should be chopped very fine (1/4 in to 3/8 in).
- Rate of filling: slow filling will reduce the rate of fermentation so that pH stays higher for longer time. Some of the problems with shrink losses are the air trapped inside the silage. This will promote yeasts and mold causing serious problems to the final product.
- Covering the silage: covering a bunker with plastic is the best choice to reduce shrink losses. For better results cover quickly after the bunker has been filled.