Understanding the fermentation process in corn silage can help producers keep their eye on the overall goal, which is producing high-quality silage to provide an excellent source of hygienic feed and nutrients for cattle growth and gain.

The ensiling fermentation is really a war between “armies” of “good” and “bad” microbes. Which side wins this microbial war determines the final quality of the feed and how stable it will be during storage and feedout.

The main determinant of the quality of silage is, of course, the quality of material at harvest. Ideally, producers should have the goal of getting their high quality, stress-free, disease-free, insect and weather damage-free corn crop cut at the optimum moisture level and stage of maturity. Then, get it chopped, processed and inoculated properly and into the pile as quickly as possible, ensuring that the material is packed to achieve at least the recommended minimum densities (at least 45 pounds as fed per cubic foot). When finished, cover and seal completely as quickly as possible.

At harvest, the microbial population on the plant can vary significantly: the use of a research-proven inoculant to ensure the “good guys” dominate is highly recommended. At this point, the aim is to ensure rapid production of lactic acid, the strongest fermentation acid, to help bring the pH down below 5 quickly. A pH of 5 or lower is a critical control point because that’s when we stop the growth of clostridia and E. coli, among other microbes, and shut down the plant’s own degradative enzymes.

During this initial fermentation stage the chemical composition of the material changes dramatically as the crop is transformed into silage. Once active fermentation is completed, the storage period begins. Provided the material remains well sealed, the only major change during prolonged storage is an increase in ruminal starch degradability. Ideally, silage should sit for eight to nine months before feeding to allow time to reach the maximum digestibility. If the silage has to be fed sooner, test starch digestibility at least once a month to make ration adjustments.

Once feedout begins, the silage is again exposed to air. This “wakes up” spoilage yeasts that were on the crop at harvest and they grow, using up nutrients and causing heating and spoilage. The higher the yeast population, the lower the silage stability, and the higher the rate of deterioration. If yeasts are likely to be a problem, consider using an inoculant proven to control them and reduce heating and spoilage.

Visibly spoiled silage should always be discarded. Studies at Kansas State University have shown that if spoiled silage is mixed into the ration there is a significant decrease in dry matter intake of beef cattle and also a significant decrease in dry matter digestibility (Figure 1),  because the spoiled silage breaks up the rumen mat, which is the site of rumen degradation.1

That’s just a peek into the process of corn silage production. Although it may seem like a simple process, there’s a lot going on and the process does need to be controlled. Using best management practices, including using proven inoculants, can help you achieve a good fermentation and produce stable corn silage with high digestibility and excellent feed value.                                                                          

To download proceedings, or watch a video of a presentation on the corn silage fermentation presented at the 2016 Husker Corn Silage Conference, visit http://www.iowabeefcenter.org/events/huskercornsilageconference2016.html. The conference was sponsored by Lallemand Animal Nutrition, the University of Nebraska Extension and the Iowa Beef Center.

For additional silage tips, visit www.qualitysilage.com or Ask the Silage Dr. on Twitter or Facebook.

1 Whitlock LA, Wistuba T, Siefers MK, Pope RV, Brent BE, Bolsen KK. Effect of level of surface-spoiled silage on the nutritive value of corn silage-based rations. Cattlemen’s Day 2000. Accessed May 21, 2015. Available at: http://krex.k-state.edu/dspace/bitstream/handle/2097/4652/cattle00pg22-24.pdf?sequence=1.