Genetic and Environmental Factors Impacting Corn Silage Fiber Digestibility

Some companies are claiming they can produce corn silage with similar fiber digestibility (NDFD) to BMR by increasing stalk diameter as a result of significantly reducing plant populations as low as 24,000 plants per acre (ppa). This document will address research findings related to this theory that a standard hybrid can be manipulated to exhibit the NDFD and dry matter intake potential of BMR genetics.

While NDFD is certainly important to cow performance, silage yield is also a major economic driver especially on dairies with a limited land base from which to harvest and transport forages.

There is typically greater silage yield potential to be found through higher plant populations as documented in many university studies (Ferreira and Teets, 2017). Of course, optimum plant population varies by soil type, soil fertility, water availability, and plant genetics. Figure 1 shows results from 2000-2008 University of Wisconsin corn silage trials indicating that corn grain yield was maximized at 38,000ppa while corn silage yield was maximized at 44,000 plants per acre and corn silage milk/acre was maximized at 41,000ppa. Milk per ton was maximized at 18,000ppa but it is unlikely any dairy could sacrifice that much yield by planting at such a low population, even if planting ear-flexing hybrids.

BMR silage genetics show a similar trend in terms of yield increasing with increasing plant population as demonstrated in a 2011 Pioneer research study (Figure 2).

Some studies have shown a small but biologically insignificant reduction in NDFD with increasing plant population. A summary of Pioneer silage hybrid studies from 2004-2007 show that 24-hour NDFD was reduced by 1-percentage point in hybrids planted from 18,000 to 42,000ppa (Jeschke and Curran, 2008, Figure 3). This small decrease would have no impact on cow performance, even if corn silage was the primary forage in the diet.

A more recent 2017 study by Ferreira and Teets (2017) examined two different standard hybrids planted in seven different fields at 55,000, 70,000, 85,000 and 100,000 ppa. This study demonstrated that planting density increased yield and while reducing stalk diameter (Figure 4), did not significantly (P>0.12) reduce 30-hour ruminal in vitro NDFD of the resulting silage (Figure 5).

A 2-year study at the Cornell University (Aurora) Research Farm in 2008 and 2009 evaluated two Pioneer (34T55 and 34A89), two DeKalb (DKC61-69 and DKC63-42), two leafy (TMF2Q716 and 2W587, Mycogen), and two brown midrib (F2F566 and F2F610, Mycogen) hybrids at planting rates of 25,000, 30,000, 35,000, and 40,000 kernels/acre (Figure 6). The researchers concluded that the DeKalb, leafy, and brown midrib hybrids had their highest yield at 35,000 kernels/acre with no real detrimental effect on NDFD and starch concentrations, whereas the Pioneer hybrids yielded best at 40,000 kernels/acre without negatively impacting NDFD (Cox et al., 2009).

The significant impact of growing environment, especially the influence of precipitation and soil water holding capacity, is well documented (Mahanna, 2010). Figure 7 illustrates the range in NDFD that one hybrid can display depending upon the unique growing environment. It is a misrepresentation of hybrid differences for any company to compare yield, starch or NDFD of hybrids not grown in the same location.

• Bolinger, D. 2010. Field study personal communications.
• Cox, Bill, J. Cherney and P. Atkins. 2009. Corn silage hybrids and plant populations. Cornell Extension Bulletin - What’s Cropping Up? Vol. 20, No.2.
• Ferreira, G and C. Teets. 2017. Effect of planting density on yield, nutritional quality and ruminal in vitro digestibility of corn for silage grown under on-farm conditions. P.A.S. 33:420-425.
• Jeschke, M and B. Curran. 2008. Plant population effects on corn silage yield and quality. Crop Insights Vol.18, No.8.
• Lauer, J. 2009. University of Wisconsin Agronomy Advice. Field Crops 28.424-62.
• Mahanna, B. 2010. Growing conditions affect silage quality. Feedstuffs. Vol. 82, No. 24.
• Soderlund, S., F. N. Owens and C. Fagan. 2013. Field experience with drought-tolerant corn. Presentation given at the Joint Annual Meeting of the American Dairy Science Association (ADSA) and American Society of Animal Science (ASAS), Indianapolis, Indiana, July 2013.