Rain Wreaks Havoc on Corn Silage Quality in 2013

This article was originally written for and distributed to farmers and other members of the agricultural industry in western New York.

Preliminary analyses are indicating that the quality of new crop corn silage is considerably lower in 2013 than in 2012. Higher fiber content, lower fiber digestibility, lower starch content, and smaller ears can all be linked back to higher than normal rainfall this year. Slower than normal dry-down also delayed corn silage harvest on many farms. However it appears that BMR varieties have weathered the storm better than conventional varieties.

2013 Corn Silage
In the November 2013 edition of Hoard’s Dairyman, Dr. John Goeser of Rock River Laboratory discusses the decreased corn silage quality in the Midwest and the Northeast, Figure 1. “Starch levels have decreased and NDF (fiber) levels have increased, decreasing energy levels. To make matters worse, TTNDFD (total tract fiber digestibility) has also dropped from last year’s crop.”

Figure 1. Midwest and eastern U.S. region corn silage crop quality from 2011 to 2013.

The data from the Northeast region included 2012 & 2013 samples from over a dozen farms in western New York, Figure 2. Samples included conventional hybrids, BMR varieties, along with some Shredlage corn silages.

Figure 2: Corn Silage Quality Google Map

These changes in fiber content and fiber digestibility are due to the higher than normal rainfall experienced in both regions. Like all plants, corn transfers water from its roots, through its xylem, and out its leaves into the atmosphere. Think of the corn plant as a giant straw. In wet years that straw needs to move a lot more water from the soil into the air. The plant senses this and reinforces the strength of the xylem by adding more cellulose (increase in NDF) and more lignin (decrease in total tract fiber digestibility) in order to handle the increased evapotranspiration load.

Despite these overall trends there were considerable differences between the BMR and the conventional varieties, Table 1. BMR samples had no change in CP content, while conventional varieties lost 0.5% on average. BMR samples also had higher CP content (~0.5% in 2012 and ~0.9% in 2013) than conventional varieties. While all corn silage had increased NDF in 2013, the BMR corn silage experienced less than half the increase (~1.3%) seen in conventional varieties (~4%). Surprisingly, the lignin content actually dropped in BMR varieties (-0.5%), but increased as expected in conventional varieties (+0.2%). BMR varieties also had increased starch content in 2013 (+1.6%) compared to the drop in starch (-3.5%) in conventional varieties. Fiber digestibility as measure by TTNDFD and Dynamic NDF kd also showed that BMR silages dropped less than conventional silages in 2013.

Table 1. BMR & Conventional Corn Silage from Western NY 2012 & 2013

*CP = crude protein %DM, NDF = neutral detergent fiber %DM, Lignin & Starch are % DM, TTNDFD = total tract NDF digestibility, Dynamic NDF kd = % of NDF digested per hour.

Besides changing the plant physiology of the corn silages, forage quality was changed by the high rainfall conditions through high losses of nitrogen throughout the region. Many farms went back in and put on 50-60 lbs/acre of nitrogen as a side-dressing or through drop-nozzles at tasseling. Numerous fields that did not receive any additional nitrogen had smaller than normal ears as a result.

Corn Silage Gets Better with Age & Attention to Detail

This article was originally written for and distributed to farmers and other members of the agricultural industry in western New York.

Leave Corn Silage in the Bunk
It is well-known that feeding “green” corn silage will result in lower milk production than “cooked” corn silage. This change in production is due primarily to the increases in starch and protein availability as the silage cures in the bunk or silo. Generally corn silage needs to be stored for a minimum of 3 weeks to complete the ensiling process. As corn silage sits in the bunk the availability of starch will generally increase up to 6 months of storage. However BMR varieties appear to buck the trend of conventional hybrids feeding poorly with little time in the bunker this year. My observations on farms in western NY that are feeding “green” BMR corn silage indicate little, if any, drop in milk production in 2013. Follow-up research is necessary to confirm if the BMR varieties are truly outperforming conventional varieties in wet years and coming out of the bunk “green,” but the initial observations are promising.

The Corn Silage Shake Down
A number of reports of poorly chopped and processed corn silage have come in from across western New York. Besides chemical analyses, using the Penn State Shaker Box and kernel processing scores to measure physical characteristics can help determine whether or not your corn silage was chopped and processed correctly. When corn silage has been chopped & processed properly most of the material will be in the middle screen of the Penn State Shaker Box, Table 1.

Table 1: Corn silage, haylage, and TMR particle size recommendations for lactating cows.

Source: Penn State University

But there is an exception to these guidelines---Shredlage. A higher portion of the particles (~30%) will be in the Upper Sieve compared to lower percentages found in normal corn silage. No sorting has been observed by dairy cows fed Shredlage. Kernel processing scores are determined by drying corn silage, running it through a series of sieves (Figure 1), and ranking by the percentage of the starch (i.e. the kernels) that pass through the 4.75 mm screen, Table 2. 

Table 2. Kernel Processing Scores & Percentage of Samples

*Corn Silage Processing Score, 551 Samples, CVAS 2006 Crop Year

Most of the corn silage has room for improvement as less than 10% of all samples have optimal processing scores. Again Shredlage corn silage is the exception to the rule as most samples have received “Optimally Processed” rankings when analyzed for kernel processing scores. The reason why most scores are lower than desired is that adjustments are often not made to the chopping equipment during harvest. 

Figure 1. Kernel Processing Score Sieves

Whether you are chopping your own corn silage or rely on a custom operator the only way to know whether or not your silage is being chopped and/or processed correctly is to get out in the bunk and measure it as it’s starting to come in. While it is too late to change this year’s silage, you can run next year’s freshly chopped silage through the Penn State Shaker Box on farm when the first load comes in and send a sample off for kernel processing score analysis at most of the commercial labs. If nothing else, get out of the tractor and down into the bunk to have a closer look at your corn silage. Using these tools and your experience will help make the necessary adjustments to theoretical length of cut and processing roll settings in order to improve the physical characteristics of your corn silage in future years.