Corn silage harvest is complete for many dairy farms across the Midwest. Reports are mostly positive in terms of yield and quality. There are certainly a few exceptions such as the damage in Iowa.
    Where did you have your cutter bar set when chopping corn silage this season? The advantages and disadvantages of high-cut corn silage have been widely discussed. There is a tradeoff between reduced yields and higher quality as more stalk residue is left in the field.
    Dr. Greg Roth from Penn State University summarized results of 11 peer-reviewed articles that compare yield and nutritional value of regular-cut corn silage averaging 7 inches to high-cut corn silage averaging 19 inches. These results will be referenced with the data presented.
    Allow me to share a few real-world evaluations on cutting height conducted the past couple weeks to satisfy producer curiosity and corroborate years of research.

Field evaluations
    Samples were collected on eight fields on multiple farms representing several corn hybrids across geographies. The starting cutter bar height ranged from 7 to 9 inches. On one farm, we did three increments of cutting height. The upper cutting height on all fields ranged from 23 to 25 inches. We inadvertently achieved a wider average cutting range than the composite of studies done at PSU. Our regular-cut corn silage averaged 8 inches and high-cut corn silage averaged 24 inches.
    In addition to raising the chopper heads in the fields, we did some further evaluation using a chipper to evaluate field corn plants. Some of this data is referenced as well.

Dry matter differences
    The bottom couple feet of a corn plant contains not only higher levels of lignin but also higher moisture levels. In addition, the ear represents a larger proportion of the tonnage in higher cuttings, and the grain is drier than stover at harvest time.
    Our high-cut corn silage averaged 7.6% higher dry matter content compared to normal cut. The PSU summary showed an average of 6% higher DM content for high-cut. With all these comparisons, keep in mind the PSU data summary had a smaller range from high- to low-cut.

Quality measurements
    All our samples were analyzed for nutrient quality through a commercial forage lab. Here is what our high-cut silage delivered, on average, compared to regular-cut silage:
    – 2.5% increase in protein (PSU data 2%).
    – 8.5% decrease in neutral detergent fiber (PSU data 7.4%).
    – 4.5% increase in starch (PSU data 5.9%).
    – 4.8% increase in NDF digestibility (PSU data 4.7%).
    – 10.5% decrease in undigestible NDF-240 hour (PSU data not reported).
    – 3.4% increase in predicted milk per ton (PSU data 5.2%).

What about yield?
    We were not able to collect accurate yield data in all situations. Where we were able to capture this, our yields averaged 26.5 tons per acre with low-cut and 23.6 tons per acre with high-cut (35% dry matter basis). This equates to just over 11% yield reduction by leaving 2 feet of stumps in the field compared to an average of 8 inches. Upon seeing the high-cut strips in the field next to the regular-cut, one producer expressed, “That’s a lot of silage left in the field.”

Future considerations
    If high-chop corn silage is being considered, more acres of silage will need to be planted to realize the same tonnage as a low-cut silage. Haylage quality can also influence the desire to shift to higher cut at corn silage harvest.
    High-chopped corn silage is not for every farm. The term high-cut also implies that we need to get to a finite 20 to 24 inches of cutting height. Moderately increasing cutting height will still move the needle on forage quality. Work with your nutritionist to decide what cutting height works for your dairy.
    I would like to thank the collaborating farms to allow me to interrupt their chopping routine and gather this data.
    Barry Visser is a nutritionist for Vita Plus.