Hybrid Selection

Corn hybrid selection is one of the most important management decisions in silage production. Selecting the correct hybrid can often mean the difference between breaking even and making a profit.

Selecting hybrids for silage production depends somewhat on whether a field is planned specifically for silage or whether the field may be harvested for grain (dual purpose). Silage types should have high forage yields and high digestibility, low fiber levels, and stover that is highly digestible. The best silage types have high grain yields because grain is so highly digestible. However, ranking for top-yielding hybrids used for silage may vary based on differences in fiber digestibility and grain-to-stover ratio. A dual-purpose hybrid should have both high grain and forage yields. For both scenarios, hybrid selection should start with identifying a group of hybrids that are adapted to the area in terms of maturity, disease and insect resistance, and drought tolerance.

Generally, higher silage yields are produced with hybrids that mature slightly later than those adapted for grain production – perhaps 5 to 10 relative maturity units later. In areas with short growing season, hybrids should consistently reach harvest maturity just before frost. Other factors, such as feed requirements, harvest timing and the potential of wet soils at harvest may dictate the selection of earlier maturing hybrids. Growers using a dual-purpose strategy may need to plant some fields to the adapted maturity to assure ripening and a limited acreage to the later types for corn silage.

Once a group of adapted hybrids is identified, evaluate them on the basis of yield potential. For those fields that are planned for silage production, evaluate hybrids based on silage yields performance. Many studies have shown that grain yield is a good general indicator of whole plant yield, that is, high grain yielding hybrids tend to have high silage yields. However, within the high grain group, there can be differences in whole plant yield and fiber digestibility, reinforcing the need to have silage data available on these hybrids. For the dual-purpose strategy, select hybrids with good grain and silage yields.

The final consideration for hybrid evaluation should be quality. Differences exist among commercial corn hybrids for digestibility, NDF (neutral detergent fiber), NDF digestibility, and protein. Most studies have shown that within a group of commercial hybrids, there will be a few with superior quality, most with average quality, and a few with significantly less than average quality. Many seed companies are developing forage quality profiles of existing corn hybrids. Select hybrids with a combination of yield and quality that maximizes livestock production per acre.

Predicting animal response and relating it to improvements in corn silage quality is complex. Differences in quality can translate into differences in animal performance. The optimum silage composition can vary depending on the type of cattle it's fed to and on the other components of the ration. For example, a high grain or high starch corn silage may be best in a finishing ration or in a dairy ration that contains a lot of good quality forage. But in a dairy ration where corn silage makes up the bulk of the ration, the same high grain corn silage may not be as desirable as a high energy, low grain silage. The best estimates of animal performance responses and supplementation costs can be obtained through forage analysis.

One approach to combining yield and quality information is to estimate a value for the feed production potential of a hybrid. The trade-off between yield and quality in selecting hybrids for corn silage production is based on the value placed on silages of different nutritional composition. The preferred method to determine the value of a forage is to value the nutritional components in the forage based on market prices of other feeds. Specifically, corn silage can be valued based on calculated market prices for energy, protein, and digestibility as measured by net energy for lactation (NEL), crude protein, and NDF. Prices of corn, soybean meal, and legume hay can be used to determine market prices for these nutritional components (table 1). The analysis must also adjust for differences in dry matter content of the fee. This method allows a valuation based on the market value of the nutritional content of the feed rather than the value of an output product. Differences in forage value calculated in this way reflect additional amounts of grain and digestibility required to equate quality differences of the forages.

Table 1. Market value ($/wet ton) of the nutritional content of average corn silage at different legume hay, corn, and soybean meal prices.1

  Legume hay prices, $80/ton Legume hay prices, $110/ton
Corn Soybean meal prices
price $240/ton $260/ton $280/ton $240/ton $260/ton $280/ton
$2.20 $14.37 $11.85 $9.32 $28.19 $25.66 $23.14
$2.40 $15.09 $12.56 $10.04 $28.90 $26.37 $23.85
$2.60 $15.80 $13.26 $10.75 $29.61 $27.09 $24.56
$2.80 $16.51 $13.99 $11.46 $30.33 $27.80 $25.28
$3.00 $17.23 $14.70 $12.18 $31.04 $28.51 $25.99
$3.20 $17.94 $15.42 $12.89 $31.75 $29.23 $26.70
1Average corn silage is 33% dry matter testing: CP = 8.8%, NEL = 0.69, NDF = 49%.

Once the values of the different hybrids have been determined, gross return per acre can be calculated by multiplying the value per ton by the yield per acre. Table 2 contains an analysis of three different corn hybrids and a calculation of value per acre for each. Hybrid A has a higher percentage of dry matter resulting in a higher value per wet ton than hybrid B. Hybrid B has a higher protein content, lower NDF content, and higher net energy than hybrid C, resulting in similar returns, even though dry matter yields were 5% higher with hybrid C.

Some research suggests that differences in cell wall or ND digestibility may affect feed intake and milk production. NDF digestibility is not routinely measured, however, and the relationship between NDF digestibility and milk production is not well documented so it is difficult to include this quality factor in estimating silage value.

Table 2. Illustration of silage value and yield trade-off.1

Hybrid DM (%) CP (%) NEL (mcal) NDF (%) Value ($/ton) Yield (T/A) Gross return ($/A)
A 39 8.2 0.77 43.3 $31.43 19 $597.17
B 33 8.2 0.77 43.3 $26.60 19 $505.40
C 33 7.7 0.77 43.3 $25.20 20 $504.00
1 Based on the following assumptions:
      Corn grain: $2.50/bushel, 88% DM, 10% CP, 9% NDF, 0.9 Mcal NEL.
      Soybean meal: $250/ton, 90% DM, 50% CP, 14% NDF, 0.88 Mcal NEL.
      Legume hay: $105/ton, 90% DM, 18.6% CP, 47.7% NDF, 0.6 Mcal NEL.

Other Corn Types

Several types of corn are available that differ in genetic makeup and may affect silage characteristics. These include high-sugar (grainless or male sterile), waxy, high-oil, brown-midrib, tropical, open-pollinated, and sweet corn. In some cases, these types are poor choices for crop production because of low yield or lodging.

High-sugar corn is a male-sterile plant with no kernel development that offers yields similar to or less than normal dent corn. Sugars accumulate in the stalk because of the lack of grain. Feeding trials have shown similar animal performance from high sugar and normal dent hybrids. The plants stay greener longer and require a hard killing frost to dry down to acceptable ensiling moistures in upright silos.

Waxy corn grain contains all amylopectin starch giving it a waxy appearance. Normal corn starch contains about 75% amylopectin starch and 25% amylase starch. Limited feeding trial data for corn silage suggest that waxy corn silage is equal to normal corn for forage quality. Aside from starch content, waxy corn is very similar to normal field corn although it tends to dry down slower, which may be an advantage when making silage or high-moisture corn.

High-oil corn has greater energy than normal corn because the calorie content of oil is approximately 2.5 times greater than that of starch. Feeding trials show higher dry matter intake, but lower digestibility than silage of normal corn. Lower yields have been associated with elevated oil levels.

Brown-midrib corn has lower lignin levels in stalks and leaves as compared to field corn. Since lignin is indigestible, the lower levels in brown-midrib corn plants make it more digestible than normal corn plants. However, animal performance in feeding trials is inconsistent. Also, field trials have shown poor early season vigor, increased lodging, delayed flowering, and poor grain yields.

Tropical hybrids are used in many areas of the Southeast for late planning or double crop corn silage. These hybrids have increased insect and disease tolerance which contributes to their higher yield performance in these situations compared to temperate hybrids. These hybrids are tall, very late maturing, and have high ear placement. They also tend to have higher ADF and NDF levels as well as higher NDF digestibility.

Open-pollinated corn is genetically variable and often susceptible to lodging. Yield potential can be up to 25% lower than for hybrids and forage quality can also be affected. Variable maturity and moisture among plants is undesirable for silage production.

Sweet corn is often available for ensiling as canning factory waste, stover, and as whole plants. Canning factory waste consists of husks, cobs, and some ears. This silage is usually lower in protein and energy than silage made from eared field corn. On a dry matter basis, its nutritive value equals that of immature field corn. Sweet corn also yields considerably less than field corn. Sweet corn stover left after removing the ears for the factory has more nutritive value than stover from mature field corn due to great leafiness, and greener leaves and stalks. Whole plant sweet corn silage is made by allowing the plant to mature before ensiling, and its feed value equals that of field corn with similar ear-to-stalk ratios. A disadvantage of sweet corn is its slow grain dry-down rate. This not only delays harvest and increases the risk of spoilage, but reduces stover quality due to increased lignin and fiber concentrations.

Testing hybrid silage performance on-farm

New hybrids may not necessarily be superior in local areas, even though their average performance over a wider region is superior. Conducting a performance test on your farm or in cooperation with neighbors using similar management practices can help you select the best hybrids for your operation. The following list outlines the basic principles used in setting up and evaluating on-farm tests.

  • Selecting hybrids. When selecting hybrids, limit the number of hybrids to no more than 10 and include two or three well-known check hybrids. Select hybrids of similar maturity.
  • Blocking. Choose a uniform area in the field. Divide the area into three blocks of equal sizes. Plant one plot of each hybrid per block, arranging the hybrids in a different order in each block.
  • Plot size. Optimum plot size will depend on the size of uniform land area, the number of hybrids, and the size of the equipment. Typically,1/10 of an acre is enough for most tests. Plots should be similar in size and border areas should be used at edges of the field.
  • Management. Manage each plot identically, keeping conditions as similar as possible to the conditions that normally occur on your farm.
  • Record keeping. Keep accurate and up-to-date records. Walk the area every few weeks during the season. Note obvious strengths and weaknesses of the hybrids plus any problems with the test. Weigh the yield of each plot, take a moisture sample, and adjust yields to the same moisture content.
  • Analysis. Calculate the averages over the three blocks to compare hybrids. A well-conducted test will have small differences among plots of the same hybrid and some large differences between hybrid averages. When evaluating hybrids, consider all important traits – such as lodging, disease and insect resistance, and drought tolerance – and not just yield.
  • On-going testing. Data collected from one field in one year may be misleading. Before planting hybrids on large acreages, collect data over two to three years and check reliable sources for more information. One year's data may be adequate to discard poor hybrids from the test. Replace discarded hybrids with new hybrids the following year.

Further Reading

Wisconsin

Note: Web resources for Wisconsin are maintained by Mike Rankin and Team Forage. Please see http://www.uwex.edu/ces/crops/uwforage/Silage.htm for an up-to-date listing.

Wisconsin Corn Hybrid Performance Trials - Grain and Silage - available in printed or spreadsheet format

Evaluating performance of corn hybrids for silage production on Wisconsin farms
by Joe Lauer, UW Extension Corn Agronomist, et. al.

Selecting Corn Silage Hybrid Maturities
by Dr. Joe Lauer, Wisconsin Crop Manager, May, 2005

Corn Silage Hybrid Selection....picking the winners so you won't be a loser      [Part 1]      [Part 2]
by Mike Rankin, Crops and Soils Agent - Fond du Lac Co.

Brown midrib corn silage for lactating dairy cows: A contemporary review
by Hidir Gencoglu, Randy Shaver and Joe Lauer, Departments of Dairy Science and Agronomy, UW-Madison

Using Milk2000 to Estimate Corn Hybrid Silage Performance
by Joe Lauer, UW Extension Corn Agronomist, et. al.  A "Focus on Forage" fact sheet

Selecting Corn Silage Hybrids and Alfalfa Varieties Using Milk2000
by Dan Undersander, UW Forage Agronomist.  Click here for the MS Power Point presentation given at the 2002 WI Fertilizer, Ag Lime, and Pest Mgt. Conf.

Milk2000: A New Way to Estimate Corn Silage Hybrid Performance
by Dr. Joe Lauer, Wisconsin Crop Manager Article, December, 2000

Corn Germplasms for Silage Uses
by Dr. Joe Lauer, UWEX Agronomy Advice, December, 1995

More Mileage from Corn Silage: Selecting Hybrids 
by Dr. Joe Lauer, UWEX Agronomy Advice, June, 1997

Brown Midrib Corn
by Dr. Joe Lauer, UWEX Agronomy Advice, March, 1997


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