University of Vermont

Corn Silage Forage Quality in Vermont for 2005 Corn Silage Forage Quality in Vermont for 2005

Sid Bosworth, Extension Associate Professor, Department of Plant and Soil Science, University of Vermont

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The following tables and graphs summarize corn silage quality data from samples tested at the University of Vermont Agricultural Testing Lab.   Table 1 gives an overall summary of 2005 compared to data collected at the same time period in 2004, while Table 2 on the next page compares quality data by dry matter content groupings (2005 samples only).  In terms of fiber and energy (ADF, NDF and NEL, NFC and starch), overall corn silage quality was slightly better in 2005 than 2004 even though the range in values was somewhat similar.

Dry matter content of corn silage depends greatly on the maturity of the corn at time of harvest often reflecting the proportion and development of kernels in the silage.   From Table 2 and Figures 1 to 4, you can see that as samples increased in dry matter content, they generally decreased in CP, ADF, and NDF but increased in starch suggesting that the leaf/stalk to grain ratio also decreased as dm increased.

Research has shown that, generally, the best milk production by diary cows fed corn silage occurs when whole plant dry matter content is between 30 and 35% or 65 to 70% moisture content (Shaver et. al. 2004).  In our summary of 2005 (Table 2), less than half (44%) all 486 samples had dry matter levels between 30 and 35%.  Harvesting at a lower dm (<30%) content often results in increased seepage, higher silage pH, lower dm intake and lower yields.   About 32% of the 2005 samples were in this category.    Harvesting too dry (> 40%) often results in poor packing, which can cause improper fermentation and poor aerobic stability.   Although NDF is lowest in this group, which would imply a higher potential dm intake, research has shown that the digestibility of this NDF would be lower than the NDF harvested at an earlier maturity (Figure 5).  Starch was highest in this group, but again its digestibility is probably low especially if the silage had not been processed (Figure 6).

Figure 1. The relationship of NDF and whole plant DM content from 2005 corn silage samples. (UVM Ag Testing Lab)
Figure 2. The relationship of NEL and whole plant DM content from 2005 corn silage samples. (UVM Ag Testing Lab)
Figure 3. The relationship of NFC and whole plant DM content from 2005 corn silage samples. (UVM Ag Testing Lab)
Figure 4. The relationship of starch and whole plant DM content from 2005 corn silage samples. (UVM Ag Testing Lab)

Figure 5.  Effect of maturity stage on 48 h NDF digestibility of corn silage. (from Hoffman, 2003)

Figure 6.  Effect of corn silage dry matter content on predicted apparent total tract starch digestibility. Top line - processed cornsilage and bottom line - unprocessed corn silage.  (from Schwab et al., 2003)

Hoffman, P.C., K.M. Lundberg, L.M. Bauman and Randy D. Shaver.  2003.   The Effect of Maturity on NDF Digestibility.  Focus on Forage – Vol. 5: No. 15, Un. of Wisconsin Extension.

Shaver, Randy.  2004. Harvest and Storage of High-Quality Corn Silage for Dairy Cows.  UN. of Wisconsin Extension.

Schwab, E. C., R. D. Shaver, J. G. Lauer, and J. G. Coors. 2003.  Estimating silage energy value and milk yield to rank corn hybrids.  J. Anim. Feed Sci. Technol. 109:1-18.

Forage Terms and Explanations Used by the University of Vermont Forage Testing Laboratory

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Last modified December 09 2005 04:39 PM

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