Corn silage refresher - Part 2: Analyzing and adjusting during harvest

The harvesters are rolling, but do you know what to analyze, how to adjust and the optimal protocols to ensure high quality silage?

Cutting date selection is only part of the procedure to obtain high quality corn silage. This article discusses important indicators to monitor when harvesting and which are determinant steps to ensure that silage quality is maintained from cutting through to covering the pile.

The first important factor to establish is cutting height. University of Delaware research reported that cutting height had a significant effect on the chemical composition and the nutritional profile of the corn silage. Increasing cutting height resulted in a decreased concentration of fiber and an increase in the concentration of starch. However, this also resulted in a decrease corn silage yield/acre.

It’s important to remember that starch is a significant energy contributor for cows but fiber is essential for optimal rumen function, VFA production and milk fat synthesis. In the referred study a small increase in milk production was reported but this did not affect the yield of milk components, which are the ultimate determinants of milk value in current markets. One recommendation is to economically analyze if the benefit of increasing milk production due to higher forage quality will offset the economic loss due to reduced yield. Michigan State University Extension recommends consulting with your nutritionist or local forage experts to determine what cutting height is appropriate for your farm-specific needs.

Monitoring and adjusting particle size and kernel processing is also important to consider throughout the corn silage harvest process. Particle size has a large influence on dry matter intake, rumen health, milk production. If particle size is larger than recommended it could reduce the packing capacity, which can interfere with the fermentation process thus reducing the quality of the silage. Increased particle size could also result in decreased dry matter intake due to physical rumen fill, which will consequently decrease milk production. On the other hand, particle size that is too small can also have negative effects on rumen health and milk production, plus it can also negatively impact milk fat synthesis and in some cases induce milk fat depression.

The recommended theoretical length of chop (TLC) will depend on the equipment used and if a kernel processor is present. For choppers equipped with a kernel processor the recommendation is to aim for ¾-inch TLC. If a kernel processor is not present, the recommendation is to reduce TLC to 3/8-inch.

Particle size can be analyzed by a laboratory, or for quicker results, on the field using a forage particle separator (see particle size guidelines).

Kernel processing is key for both silage quality and starch digestibility thus, improper processing of the kernel will negatively impact both. Multiple approaches can be used to track kernel processing. Performing this analysis will allow for adjustments that can optimize silage quality. A quick qualitative analysis can be performed on the field using a 32 ounce cup. Fill the cup with chopped forage (corn silage) then spread the sample over a clean surface. Browse through the entire sample and record the number of half kernels or larger. Pay special attention to the number of whole or nicked kernels. If using this analysis, the goal is to find less than two half or whole kernels per sample (32 ounces). A more standardized process is the corn silage processing score or CSPS (summarized CSPS procedure). Is important to remember that starch concentration is one of the important reasons to feed corn silage thus ensuring starch availability is key.

It's also important to limit silage exposure to oxygen because prolonged exposure can negatively affect the silage fermentation process. To avoid this, two important factors to monitor are filling speed and packing density. Filling speed becomes especially important with bunker or a drive-over pile because a large part of the silage is exposed to oxygen while filling and packing, when compared to silage bags or upright silos. The recommendation from MSU Extension is to chop, fill and pack as fast as possible. To minimize exposure, it is important to have excellent communication and coordination between the chopper, transporting trucks and packing tractors. It’s also key to remember that filling speed should NOT occur at the expense of proper packing. Research has shown that even 48 hours of delayed exposure of the silage to air can have a negative effect on silage fermentation and important quality measures such as pH and lactic acid values at feeding time if the harvest takes longer than 48 hours, temporary cover the silage to decrease air exposure time.

When it comes to packing, the number one rule is “Pack, Pack and Pack again”. It is important to ensure proper packing as it will be vital to prevent silage storage losses. This follows the same rationale as filling speed. The main goal is to minimize oxygen exposure within the silage. Multiple processes that will decrease the quality of your silage occur in aerobic conditions (presence of oxygen) hence, proper packing significantly reduces oxygen-containing air pockets that can interfere with the fermentation process.

To evaluate optimal packing MSU Extension recommends measuring the packing density of the silage. The research based recommendation is to aim for at least 14-15 pounds of DM per cubic feet. Calculating packing density also provides additional information that is useful for feed inventories and feed planning programs.

The final factor to protect the quality of your harvest is covering. Proper covering is key to maintaining anaerobic conditions (oxygen free) required for fermentation and nutrient preservation. Additionally, proper covering protects silage from losses due to rain and other environmental factors. To prevent oxygen exposure, the silage should be completely covered. If using plastic, the rule is that thicker plastic (6 to 8.5 mil) provides less permeability to oxygen.

Newer technologies include the use of oxygen barrier films that allow additional protection from oxygen. Independent of which covering film is selected, the process must include securing the film over the silage and adding weight to prevent air pockets between the film and the surface of the silage. The majority of the losses occur in the top one to two feet of the pile. This can be prevented by adding weight to the top of the film. Half tires that prevent water pooling spaced evenly throughout the pile, close enough that tires are touching each other are recommended to achieve this purpose. As distance between the tires increases, so does the risk of spoilage in the surface of the feed. Finally, the borders of the drive-over piles of silage or bunk ends, should be secured using tires or sand to prevent losses.

In summary, it is important to properly manage the corn silage from chopping to covering to optimize quality and feeding value. Monitoring and adjusting during harvest can make a big difference in the quality of the feed. However, ensuring adequate silage fermentation is key to maintain feed quality and prevent losses during the ensiling process. This is achieved by effective packing and covering to minimize oxygen exposure.

This article is the second in a series of three that covers corn silage harvest from the decision of when to cut and when to feed the silage.

Additional articles in this series:

Corn silage refresher – Part 1: How to set your cutting date

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