Corn silage is a moving target

The 2022 corn silage harvest is in the rearview mirror. The dry fall provided an ideal harvest window for many growers and allowed them to achieve dry matter targets. What are our expectations of animal performance with this crop? We’ve heard reports of new corn silage feeding quite well in some areas and not so well in others. An array of factors might help explain this variation, including weather, plant genetic variation and agronomic practices such as planting dates, population, fertilization and fungicide application.
Last year’s corn silage harvest can provide perspective on some of these factors. Just over a year ago, nutritionists, dairy producers and cows were trying to figure out how newly harvested corn silage was going to feed – an annual phenomenon with incredibly important implications.
A wide range of storage options and logistics dictate when a farm will need to transition from fully fermented corn silage into silage from the new harvest season. This timeline ranges from feeding the day of harvest to several months of carryover and fermentation time. Allowing adequate storage time for wet corn is the greatest supporter of starch availability. Prolamin-zein proteins encapsulate corn starch and act as a barrier to digestion. Over time, protease enzymes (produced by proteolytic bacteria) break down this protein matrix, making starch more available. The wetter the corn source, the quicker this process occurs and the sooner the feed will reach its full starch digestibility potential.
Dairyland Laboratories Inc. recently summarized nearly 12,000 corn silage samples for the past three years across Minnesota. Results show a wide range in fiber and starch content as well as fiber and starch digestibility. In general, the 2021 crop was lower in starch percentage and higher in fiber digestibility. Starch digestibility seemed to take longer to reach its full potential and, in most cases, never did reach levels achieved in the previous few years.
Historically, kernel maturity of approximately half milk line would correlate to about 65% whole-plant moisture. This has not been the case for many farms the past couple years. Dr. John Goeser with Rock River Laboratory Inc. has defined this change as a “moisture and kernel maturity disconnect.” Goeser said the growing season and conditions have a major impact on moisture, maturity and overall quality. He also pointed out that improved agronomic practices and healthier plants are influential factors. Examples such as better stay-green, drought tolerance or improved fungicide application strategies are likely resulting in healthier plants and greener tissue as the kernels mature and progress toward black layer.
For many in the Midwest, the average rainfall in 2021 and 2022 were similar and deficient throughout much of the growing season, but we certainly had exceptions to this trend in some areas. This is what makes it difficult to paint with a broad brush that corn silage across an entire region will perform equally.
Early indications from lab analysis show an improvement in the rate of starch digestibility in 2022 corn silage over the 2021 crop across comparable time periods. This can be seen in lab analysis with both seven-hour starch digestibility and starch Kd rate, which is a measurement of the rate of starch digestibility. Time will tell how extensively this pattern continues.
The one thing we know for certain about future corn silage harvests is they will be different from the past. It is likely we will continue to see a trend for kernel maturity to be well past half milk line at harvest with some of the agronomic practices designed to promote a healthier plant. This will require closer monitoring of whole-plant moisture at harvest along with greater emphasis on kernel processing.
    Barry Visser is a nutritionist for Vita Plus.