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Stretching Corn Silage Supplies

Updated September 12, 2019

Alvaro Garcia

SDSU Extension Agriculture and Natural Resources Program Director & Professor

Color-coded map of South Dakota and other Midwestern states. Colors indicate a higher risk of unplanted areas in Eastern and Northeastern South Dakota.
Figure 1. Corn acres at risk. Model developed by Gro Intelligence that ranks corn acreage from 0-20. The higher the number, the larger the risk of unplanted areas. Courtesy of North American Custom Harvesters.

During the 2002 drought there was a need to stretch corn silage supplies as a result of the drought that affected the U.S. Now we deal with the opposite scenario, where excessive spring rains have not allowed farmers to get to the fields. In both situations livestock producers face challenges. Reduced tonnage or quality of corn silage available can be expected, either because of reduced acreage and/or the crop not getting enough rain at critical growth stages later on. There is also the possibility that corn kernels will not fill soon enough for optimum starch content, if the growing season ends up being too short.

Whatever the scenario, livestock producers will need to find ways to stretch their corn silage inventory. Adequate corn silage quality needs to be the number one concern in order to improve animal performance, be it milk production or weight gains. Under these conditions it is also likely that alternative forages such as good quality hay will be in demand, commanding also higher prices. If on the other hand, producers purchase forages with an RFV value below 140, this can negatively impact animal performance.

An unfavorable international marketing environment for corn and soybeans has resulted in lower price co-products. Improving the energy density of the diets by using feedstuffs such as soy hulls and/or distillers’ grains, is a very economically attractive alternative.

Stretching Corn Silage Supplies

Provided the farm has still some corn silage in storage, it is imperative to start now stretching its use. The goal is to make minimal dietary changes now, in order to avoid drastic changes later when we run out of last year’s silage. This approach leads to little changes in animal performance if at all. The following steps are a guideline intended to be able to stretch corn silage stocks.

Make an inventory to have an idea of how long corn silage will last.

Research from the University of Wisconsin and Cornell University suggest that for adequate preservation corn silage needs to be packed at or greater than 14 lbs. of dry matter per cubic foot. To verify one’s silage is within these parameters, cut a cubic foot and weigh it. Let’s use the figures of 14 lbs. per cubic foot and the usually recommended moisture of 65%. We need to test the DM of the silage either with a Koster tester or a microwave. A cubic foot of silage with 35 percent DM and weighing 40 lbs. will have 14 lbs. of DM per cubic foot (40 x 0.35 = 14 or 14/.35 = 40).

To calculate how many pounds of silage there are in the bunker multiply:

Length (feet) x width (feet) x depth (feet) x density (lbs./ feet3).

For example, a bunker 100’ long by 30’ wide and an average height of 12’ will have:

  • 100’ x 30’ x 12’ = 36,000 feet3
  • 36,000 feet3 x 40 lbs./ feet3 = 1,440,000 lbs. silage
  • 1,440,000 lbs. silage / 2000 lbs./ton = 720 tons of silage.

To feed 500 animals at 30 lbs. per head (500 x 30 = 15,000 lbs.), there is enough corn silage for 96 days (1,440,000/15,000 = 96).

Use different forages in your ration at rates related to their availability to minimize drastic ration composition changes later on. Testing forages for nutrient content and nitrates will help re-balance the diet.

If you determined you will run out of corn silage before the new crop (remember to allow for 21-30 days of fermentation!) then start stretching the silage now, to avoid sudden changes later. Don’t disregard using blends of other forages with co-products to increase their quality! Again soy hulls and distillers’ grains are great choices! Do not underestimate in advance the value of other feedstuffs such as ditch hay or other lower quality hays whose value can be upgraded with the co-products mentioned.

Because of their high fiber and protein content, the use of distiller’s grains can help stretch out your forages, decrease feed costs and improve the nutrient content of the diet. Soy hulls can also help out by providing some fermentable fiber to the ration. Researchers at the Dairy and Food Sciences Department tested ensiling corn plants-wet distillers’ grains combinations at 75:25 and 50:50 ratios. The crude protein content was 15.6 and 20.7 percent for the 75 and 50 percent corn silage blends, respectively. In spite of the high pH of the green chopped corn plants (5.7) the initial pH of both blends was 4.6 and 4.0 for the 75 and 50 percent chopped corn plants, respectively. This was attributed to the low initial pH (3.1) with which the wet distillers came from the ethanol plant. By day 14 in the silo-bag, acetic acid concentration in both blends exceeded 3 percent of the dry matter. By day 129 the acetic acid concentration on the 75 percent chopped corn plants blend reached 5.7 percent, a value similar to that observed by University of Wisconsin researchers in bacterium-inoculated, high acetic acid silages. The low pH and high acetic acid concentration resulted in adequate preservation as well as improved “shelf-life” in the feed bunk.

Using ditch hay to feed cattle is a common practice across the U.S. It provides livestock producers with a source of readily available forage which can be very useful particularly during feed shortages. Assessing the feeding value of ditch hay however poses challenges since it is highly variable in nutrient content. The reason for this variability however doesn’t seem to be as much the plant species composition, but rather the time of harvest. During 2015, NDSU Extension analyzed 182 samples of harvested ditch hay from across the state.

The results showed that most of the ditch hay consisted of cool-season grasses, predominantly smooth bromegrass. The best compromise between yield and quality appears to be during early July. The average values also show more mature brome grass hay to contain 10% CP and 55% TDN.

Table 1. Nutrient content of ditch hay samples (n=182)
Item Average Minimum Maximum
Dry Matter 91.4 83.7 95.6
Crude Protein (CP) 8.5 5.9 17
Neutral Detergent Fiber (NDF) 65.1 35.2 73.2
Total Digestible Nutrients (TDN) 52 34.8 58.5
Source: Modified from 2016 North Dakota Beef Report
Table 2. Typical composition of brome grass fed to cattle (All values on a DM Basis)
Feedstuff DM
Brome Grass
Fresh Immature
32 15 - 4.1 28 33 54 10 0.4 0.39 2.7 0.2 - 64 1.28 0.64 0.36
Brome Grass
89 10 - 2.5 35 41 69 9 0.5 0.23 2.5 0.16 17 55 1.1 0.54 0.21
Source: Modified from Colorado State University, 2017.
Bar graph showing crude protein levels in relation to harvest date. Levels are highest befor July 1 and gradually decrease as they approach Auguest 15 and later. The average level is 8.6.
Figure 1. Crude protein in ditch hay by harvest date. Source: Modified from 2016 North Dakota Beef Report, NDSU.

Based on the data available it seems safe to formulate diets using conservative values for ditch hay of 8.5% CP and 52% TDN as reported by NDSU.

— Alvaro Garcia, SDSU Extension Agriculture and Natural Resources Program Director & Professor

Testing your forages will be particularly important with this season’s corn silages, as they will be highly variable in moisture as well as grain content between farms.

Try to avoid as much as possible sudden changes in ration composition due to forage shortages. Concentrates and co-products can be shipped relatively inexpensively, bulky feeds such as hay on the other hand, are more expensive to transport and we can only expect prices to go up during the next few months. Check with your SDSU Extension field specialists. They can help balance your diets in order to stretch out your forage supplies.