Corn silage digestibility: Can we make a difference? (Pat Hoffman)
Click here to download Hoffman’s PowerPoint presentation.
By Pat Hoffman, Vita Plus dairy technical specialist
Today’s high-producing dairy cows consume copious amounts of calories to sustain milk production and no forage is better suited to provide calories than corn silage.
As discussed at the Vita Plus Custom Harvester Meeting, corn silage is unique in the world of forages, containing a source of digestible NDF as well as digestible starch. Research has demonstrated that the digestibility of both the NDF and starch fractions can be quite variable. Because corn silage NDF and starch digestibility can vary, “the corn silage world” is filled with facts, fictions, rumors, and allegories as to what management practices can be done to improve corn silage digestibility.
Improving corn silage NDF digestibility
Considering the full scope of agronomic practices, hybrid selection would be a clear winner in improving NDF digestibility in corn silage, but hybrid selection comes with boundaries.
Selection and use of BMR-type hybrids has consistently yielded corn silage with greater NDF digestibility and, when fed to dairy cows, consistently improves dry matter intake and milk yield. Data summaries from commercial forage testing laboratories suggest BMR corn silage hybrids have in vitro NDF digestibility values 10 percentage units greater than normal corn hybrids.
It is known that differences in NDF digestibility occur within normal corn hybrids, but a universal system does not exist within commercial seed companies to evaluate normal corn hybrids for silage characteristics.
University silage evaluation trials for NDF digestibility are very valuable, but often a normal corn hybrid is only evaluated for one or two years before it is replaced with a new hybrid. Agronomists recommend evaluation of corn hybrids over multiple years and locations to truly evaluate genetic characteristics of NDF digestibility.
In regard to other corn silage management practices, only early harvest dates have shown to improve NDF digestibility. Agronomic practices such as planting date, row spacing or plant population have little influence on corn silage NDF digestibility.
Improving corn silage starch digestibility
Two true-tested management practices improve corn silage starch digestibility: kernel processing and length of fermentation.
Research data clearly demonstrates the benefits of kernel processing of corn silage. Processing corn silage to achieve kernel processing scores of 60 to 70 percent appears reasonable. But, perhaps more importantly, the goal of kernel processing should be to simply avoid whole corn kernels in corn silage.
New systems to process corn silage are in development. Research data suggest Shredlage® processing systems may improve kernel processing scores and ruminal corn silage starch digestibility in lactating cows. Other dynamic kernel processing systems are being developed and more improvements in corn silage kernel processing may be on the horizon.
Finally, intensity and duration of silage fermentation greatly improves corn silage starch digestibility. Proteolytic activity during fermentation degrades proteins that encapsulate starch, making corn silage starch more available and more digestible with advancing ensiling time.
Knowing this biology is important because it tells us to “do everything we can to promote greater fermentation in corn silage.” The laundry list of management practices includes:
- Harvest at the proper moisture content.
- Use a research-proven inoculant like Crop-N-Rich Stage 2, which improves upfront fermentation as well as aerobic stability.
- Pack, pack and pack some more.
- Properly cover bunkers or piles with high-quality plastic covers such as Silostop.
Feed quality and nutrition
Forage storage and management