Corn silage is hopefully just around the corner, which means some crucial decisions must be made to achieve a year’s worth of success with this crop. Knowing the past year’s growing season will help you make the right decisions this fall to put up a high-quality silage crop that will be fed for the upcoming year.
To high chop or not?
The amount of rainfall the silage crop received from when it went in the ground to when the corn tassels helps you predict much of the fibre digestibility of the silage. In years with above-average rain, the crop will have lower digestibility than in a drier year. This trend is even seen in brown midrib (BMR) corn crops. This decrease in digestibility is attributed to an increase in lignin production in the plant, a part of the cell wall that is indigestible in the rumen.
Considering this year’s corn silage growing environment, you can both predict the quality of the crop to come and have the right conversations with your advisers about controllable factors like cutting height.
High chop has two distinct impacts on corn silage quality. The first is that it influences the stalk-to-ear ratio, concentrating the amount of starch in harvested silage. The other potential impact is an increase in digestible NDF (dNDF).
A 2003 review from Wu and Roth at Penn State looked at 11 published studies that examined high-chop corn silage and found a 6% increase in starch and a 6.7% increase in dNDF when increasing cutting height from 7 inches to 20 inches.
However, further research on high chop from the University of Idaho and Pioneer found the scale of impact is largely influenced by hybrid genetics and as mentioned, environment. Some fieldwork has found increasing the cutting height of corn silage by 4 to 6 inches will result in a yield hit of around 1 ton at 30% dry matter. The effectiveness of the increased cutting height is very dependent on growing season and genetics, so the best way to determine if high chop is worth the decreased yield is to chop plants after tassel, at different heights, and send them away for nutrient analysis.
Review the results and have a conversation with your adviser team to consider the value of the yield loss to the value of the improved quality.
One scenario where high chop does not make sense is in BMR corn. This crop will already have an improvement of 6 to 10 points of dNFD over non-BMR corn through its genetic mutation alone.
Late-season plant health
Another factor with significant influence on quality is the late-season health of the corn crop. If a disease sets in, it will consume the more digestible portions of the corn crop, concentrating the undigestible fibres (uNDF). Disease eliminates a plant’s ability to photosynthesize, which can slow down its starch accumulation, a valuable nutrient most strive for more of.
Finally, heavy disease pressure can influence harvest timing as it changes the rate of dry-down from the normal predictive pattern. At this point in the growing season, heavy disease pressure is out of your control, but as you harvest, it is important to monitor fields for any signs of disease and have a discussion with your management team about what can be done next year.
Hybrid genetics can have an influence on a crop’s ability to handle disease, and depending on the growing season, you can look to apply a fungicide to the crop to manage the risk of disease pressure.
Making starch available
Dr. Randy Shaver from the University of Wisconsin estimated when corn silage is improved from only adequately processed to optimally processed, nearly one extra litre of milk can be produced from the available energy.
Achieving excellent kernel processing is not a new concept, but one that sometimes gets missed in the heat of the harvest. It is important to make sure you take the time to confirm you do a good job of making the energy you spent all growing season nurturing available to the cows.
Looking at residual silage from last year, take a moment to evaluate last year’s performance. Using a litre-sized container, grab some of the silage and look for any whole or half kernels, aiming for a count under four.
The same process can be used in-harvest to make sure targets are met. When you delay harvest timing to capture more starch accumulation in the kernel, it is important to ensure you have a properly set up kernel processing unit and that it is allowed to do its job.
The basics of quality silage remain the same year over year, but understanding the factors that challenge those basics will allow for the fine-tuning of management and provides a constant forage source for your dairy herd, not just throughout the year, but in each subsequent year as well.
References omitted but are available upon request by sending an email to the editor.
