Álvaro García
Corn silage remains the single most important forage in many dairy production systems, providing a substantial proportion of dietary energy through a combination of fermentable fiber and starch. While hybrid selection, harvest timing, and ensiling practices have received considerable attention, cutting height at harvest continues to be debated as a management strategy to improve silage quality. Raising cutter bar height is often promoted to increase starch concentration and digestibility, but it also carries tradeoffs in dry matter yield and whole-farm efficiency. Understanding the true impact of cutting height requires separating changes in plant composition from effects on fermentation and animal performance.
This article reviews the biological and practical consequences of corn silage cutting height on nutritive value and ensiling outcomes, clarifies common misconceptions about fermentation effects, and concludes with a summary of recent evidence from a meta-analysis published in the Journal of Dairy Science.
What changes when cutting height is increased
Raising cutting height primarily alters the proportion of plant fractions harvested, rather than fundamentally changing the nature of the corn plant. The lower stalk contains a greater proportion of structural fiber, higher lignification, and lower starch concentration than the upper stalk and ear. When cutter bar height is increased, a larger fraction of lower stalk tissue is excluded, resulting in corn silage with higher starch concentration, lower neutral detergent fiber (NDF), and modestly improved fiber digestibility.
Multiple studies have shown that this shift in composition can increase the energy density of silage on a dry matter basis, due to a higher grain-to-stover ratio. However, these improvements occur alongside a reduction in dry matter yield per hectare, as a non-trivial portion of the plant biomass is left in the field. From a nutritional standpoint, this creates a classic tradeoff: higher quality per ton versus fewer tons harvested.
Importantly, these changes reflect physical separation of plant tissues, not improvements in intrinsic digestibility of the remaining stalk. Fiber that is harvested does not become inherently more digestible; rather, less digestible material is excluded.
Implications for animal performance
Animal response to increased cutting height has been variable across studies and production systems. In some cases, higher cutting height has been associated with modest increases in milk yield or milk component yield when diets are otherwise limiting energy density. In other situations, particularly where starch supply is already adequate, responses have been minimal or absent.
From a whole-farm perspective, improvements in milk per ton of silage do not necessarily translate into improvements in milk per acre. Because dry matter yield declines as cutting height increases, farms must consider whether the nutritional benefits justify the loss of harvested forage, particularly in land-limited systems or where replacement forages are costly.
Thus, cutting height should be viewed as a strategic decision, not a universal recommendation.
Cutting height and silage fermentation: What it does—and does not—do
A common misconception is that increasing cutting height improves silage fermentation. Cutting height has limited direct influence on fermentation compared with other factors such as dry matter concentration at harvest, particle size, packing density, oxygen exclusion, and epiphytic microbial populations.
Raising cutting height can slightly increase whole-plant dry matter concentration by excluding wetter lower stalk tissue, which may indirectly influence fermentation rate and acid production. However, this effect is typically small relative to the influence of harvest maturity and kernel development. Studies consistently show that well-managed silage can ferment effectively across a wide range of cutting heights when dry matter and packing are appropriate.
In practical terms, cutting height should not be relied upon as a primary tool to correct fermentation challenges. Ensiling management remains the dominant driver of fermentation quality.
While cutting height does not fundamentally alter fermentation biology, it can serve as a tactical management tool under specific conditions. Garcia and Díaz (2017) discussed the use of increased cutting height in drought-stressed corn to reduce the inclusion of lower stalk tissue, which may contain elevated nitrate concentrations and lower digestibility. In such situations, raising the cutter bar may help manage forage safety and feeding value, even though it does not change the ensiling process itself.
This applied perspective reinforces a key point: cutting height decisions should be contextual, driven by agronomic conditions and feeding goals rather than generalized expectations of improved fermentation or dramatic performance gains.
Insights from a recent JDS meta-analysis
A comprehensive meta-analysis by Diepersloot and colleagues, published in the Journal of Dairy Science in 2025, provides the most rigorous synthesis to date of cutting height effects on corn silage yield, nutritive value, and fermentation characteristics.
Across a wide range of studies, the authors confirmed that increasing cutting height consistently reduces dry matter yield while increasing starch concentration and decreasing NDF concentration. Improvements in fiber digestibility were modest and variable, reinforcing the concept that cutting height alters plant fraction harvested rather than fiber quality per se.
Importantly, the meta-analysis found limited and inconsistent effects of cutting height on silage fermentation parameters, including pH and organic acid profiles, when silage dry matter concentration was within recommended ranges. This supports the view that fermentation outcomes are driven primarily by harvest maturity and ensiling management rather than cutter bar height.
The authors concluded that while increased cutting height can improve silage nutritive value on a per-ton basis, the accompanying yield loss must be carefully weighed against feeding benefits. From a systems perspective, cutting height should be optimized based on forage inventory needs, land availability, and ration formulation objectives rather than assumed to be a universally beneficial practice.
Conclusions
Raising cutting height in corn silage harvest predictably shifts silage composition toward higher starch and lower fiber concentrations, with modest improvements in digestibility but clear reductions in dry matter yield. These changes do not fundamentally improve silage fermentation and should not be viewed as a substitute for sound ensiling practices.
The best available evidence indicates that cutting height is best used as a context-specific management lever, not a default recommendation. Its value lies in targeted applications, such as managing forage quality under stress conditions or fine-tuning ration energy density, rather than in broadly improving fermentation or animal performance.
As with many nutritional decisions, the key question is not whether cutting height can improve silage quality, but whether it improves system-level efficiency under a given set of constraints.
The full list of references cited in this article is available upon request.
© 2025 Dellait Knowledge Center. All Rights Reserved.
