Corn silage harvest is a complex system
|By Chris Wacek-Driver|
The author owns and operates a forage consulting business, Forage Innovations LLC, in Bay City, Wis.
A system is defined as a group of interacting, interrelated, and/or interdependent elements forming a complex whole. Making corn silage, on the surface, seems like a simple process; however, if you strive to harvest quality silage, you will recognize it is anything but simple.
With its mixture of stover and grain in variable amounts, corn silage presents some unique harvest challenges, particularly as it has become a larger part of many cropping systems and livestock diets. The process can become overwhelming when crop and hybrid characteristics, changing environmental conditions, and machinery and human factors are considered.
Human nature’s tendency often takes complex systems and complicates them further, rather than simplifying the process. The clear definition and separation of goals versus objectives in a system will help to ensure the likelihood for success.
Let’s take a look at an example. If the end goal is to obtain high-quality silage that can efficiently and economically be digested to produce meat or milk, three key objectives to meet that goal might be:
Look at the whole system
Optimization of a system depends on orchestrating all the elements to achieve the end goal. If too much focus is put on one objective, such as processing the grain correctly, it can have negative consequences on other interrelated or competing objectives. In such a way we lose sight of the overall goal. In other words, we get lost in the weeds and miss the big picture.
Look at the overall system and the goals before distilling the system down into a single variable. Let’s look at what can happen when laser focus is put on only one objective of the system and how it can affect other components.
Two primary factors in the kernel inhibit optimum ruminal starch digestion. They are the hard, outer seed coat and the protein matrix surrounding the starch granules. Reducing the particle size of the kernel increases the surface area available for microbial attachment, thus enhancing starch availability. The twin processes of fermentation and time help break down the protein matrix surrounding the starch granules, adding to starch availability.
To measure the reduction of particle size, a laboratory test called the kernel processing (KP) score was developed specifically for fermented corn. This test specifies utilization of an oven-dried sample, and involves shaking corn silage through a specific set of sieves. Theoretically, starch digestion improves with a smaller particle size and higher KP score.
Processors are better
What began in the early 2000s with kernel processors set up to barely nick or crush portions of the kernel, attaining dismal processing scores, has evolved into newer processors with more aggressive rolls and differentials. Set up properly, these processors can shatter the corn kernel and achieve KP scores of 70 or better.
However, what was developed as a lab test for fermented corn is now being used as a tool for fresh silage. Recent ongoing research and field data has substantiated that with time and fermentation, the KP score will rise approximately 5 to 10 units. While fermentation may not rescue poorly-processed corn silage (a 60 or lower processing score), it plays a key part in boosting starch digestibility over time. Kernel maturity (moisture) and endosperm characteristics are also key factors.
If the optimal moisture window is missed and the corn silage is too dry, no amount of particle size reduction will make up for the reduced efficiency of starch availability that comes with optimal fermentation and time.
Don’t over process
In the field, some are striving to have a fresh KP score of 70 or 80. This objective can conflict with other key objectives and result in missing the mark on our true end goal. The time-sensitive nature and importance of corn silage harvest dictates the system proceeds as efficiently and economically as possible. Even with newer processors equipped with higher differentials and more aggressive rolls, reducing particle size comes at a significant cost in the form of power and fuel consumption.
Perhaps more important is that additional time is required to harvest. Chasing the objective of a high fresh corn silage KP score can result in a 30 to 40 percent reduction in harvested tonnage from what the equipment and a properly designed system is capable of harvesting. Additionally, it places added stress on machinery parts and the human component when breakdowns further delay harvest.
This overemphasis on particle size reduction can overshadow the objective of putting silage up at the correct moisture. If the process slows too much, and the moisture window is missed, the costs are reflected in not only reduced efficiency and economics, but also reduced starch availability due to suboptimal fermentation.
It is important to keep in mind that the KP score was a laboratory test developed for fermented rather than fresh silage. A case study referenced in Hoard’s Dairyman (August 25, 2014) substantiates field observations made by the author along with summaries done by Dairyland Labs and Rock River Labs. There appears to be significant interactions with KP score and both whole plant and kernel moistures.
A goal of at least 60
Fine particulate starch, clinging to the stover fraction in wet corn silage, may exert negative influences on the KP score, yet biologically has no adverse effects on ruminal digestion. Recent conversations with Randy Shaver (University of Wisconsin), Luis Ferraretto (University of Florida), and other key field staff would suggest a fresh KP score of 60 or better should meet the objective of adequate particle size reduction while still achieving the end goal. Similar to other tests, multiple samples need to be taken to determine a true KP score.
In summary, define key goals and objectives to optimize harvest results. Keep the end goal within the goal posts and make sure all key objectives are met. This will help ensure a profitable and efficient corn silage harvest.
This article appeared in the August/September 2018 issue of Hay & Forage Grower on pages 12 and 13.
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