Dealing with Immature Corn Silage
Corn planting was delayed due to a wet spring and growth was severely slowed by cool temperatures during the early summer months. It is likely that many corn fields will not make the proper stage for corn silage and understanding how to handle immature corn silage will be critical.
Harvest Timing and Frosted Corn
Timely harvest of corn silage is one of the most critical factors affecting forage quality. To ensure maximum yields of dry matter, nutrients per acre, palatability, intake, and minimize storage losses, corn should be harvested at 35-30% dry matter. Immature corn silage due to late planting will be at increased risk for frost damage, which occurs when temperatures stay below 32°F for a few hours or 28°F for several minutes. The stalk and grain are less susceptible to frost damage as the thicker tissue retains more heat than the leaves, which are the most susceptible to damage.
After a frost, immature corn will most likely be too low in dry matter content for direct chopping. If possible harvesting should be delayed until the plant is above 30% dry matter. Harvesting the plant at low dry matter content will alter fermentation, increase silage runoff, and could potentially decrease feed intake. To avoid seepage losses and risk of an undesirable fermentation, it will be necessary to allow the immature crop to stand in the field for several days following a frost to dry down. After a frost, moisture content is harder to determine. Frost damage turns leaves brown and creates an illusion of rapid dry down, but the plant will have a lower dry matter content than it appears to, as higher moisture content remains in the stalk and ear. Even experienced farmers who can easily estimate the moisture content for a normal corn crop might underestimate the moisture of immature corn.
Remember frozen immature corn will not dry down any faster than unfrozen corn. The only sure method to determine dry matter is to chop a small amount of and obtain a moisture determination (microwave method or Koster Tester) to know when the crop is nearing the desired 35-30% dry matter. As a rule of thumb, whole plant moisture normally decreases by 0.5% per day.
Storage
Plant material of 30% or slightly higher dry matter can be more effectively stored in a horizontal bunker or stack without excessive seepage losses than in an upright silo structure. Packing, covering, and particle size guidelines used in harvesting normal corn silage should be followed for immature corn silage. If possible, store immature corn separately from high quality corn silage. Very immature corn silage should be fed to animals with lower nutrient requirements. Under the best of conditions, inoculants are generally not necessary for corn silage, however, this may be a year to consider their use. For more information on the use of inoculants, see “Inoculants for Haylage and Corn Silage” at: http://pss.uvm.edu/vtcrops/?Page=articles/haylage.html
Feed Quality
Immature corn at the dough state will yield 65-85% of normal silage yield, and slightly immature frost damaged corn that has dented can still produce good quality silage. The table below shows that while yields are decreased, overall energy content can be similar to mature silage. However, starch levels are likely to be lower.
Immature corn will also be higher in protein than those of a fully matured crop. It is not recommended to add non-protein nitrogen (NPN) sources if the plants did not reach milk stage because seepage can concentrate NPN in the lower portion of the storage unit. After a frost, if the leaf material is dead but the stalk and roots remain alive, there is a chance nitrates will accumulate in the lower stalk. Increasing the cutting height will lower dry matter but increase silage quality since the lower stalk has the lowest digestibility and highest nitrate levels. Field losses will increase with time so producers need to balance harvest losses against fermentation loss and quality problems associated with wet silage.
It will be important to test forage made from immature corn as there will be a large variation from the nutrient content that might be expected. If you are going to feed a significant amount of immature silage to lactating cows, it will be worthwhile to obtain a fermentation analysis that includes silage pH, ammonia, titratable acidity, lactic, acetic, proprionic, butyric and isobutyric acids.
If you will be selling silage, the following resource has information regarding negotiating the value of immature corn silage: http://corn.agronomy.wisc.edu/WCM/W158.aspx
More information on managing immature silage can be found in the following resources:
“Inoculants for Haylage and Corn Silage” by Heather Darby and Sid Bosworth, UVM Extension. http://pss.uvm.edu/vtcrops/?Page=articles/haylage.html
“Considerations for Working with Immature Corn Silage” by Cornell University Cooperative Extension. http://www.thatscooperativeextension.org/documents/ag/ImmatureCornSilage.pdf
“Managing Immature and Frosted Corn Silage” by Heather Darby and Sid Bosworth, UVM Extension. https://pss.uvm.edu/vtcrops/articles/ChoppingImatureCorn.html
“Negotiating the Value of Immature Corn Silage” by Joe Lauer, University of Wisconsin. http://corn.agronomy.wisc.edu/WCM/W158.aspx