With the high-interest costs of the 1980s and economics favoring higher-energy rations with a faster turnover, many feeders transitioned to more energy-dense rations.
Now, however, it is common to witness lower-quality forages being used in both growing and finishing beef cattle. With the current economy and limited range and forage availability, is it time to reconsider corn silage?
The Aug. 13 USDA corn production estimate for 2014-2015 was 172 million bushels higher than last year, for a record 14,032 million bushels. The first survey-based corn yield forecast, at a record 167.4 bu per acre, is up 2.1 bushels from last month’s trend-based projection.
The high projected volume should mean lower prices, which could be a real boon to producers facing other challenges to the bottom line.
Most of the range and pastureland located in the western U.S. that has been hit hard by the drought has not fully recovered and will not do so until the depleted root reserves have a chance to recover.
While beef retailers and food service operators may hope for lower beef prices, the lesson from the last six months is to prepare for higher prices; cattle numbers will not increase any time soon while the U.S. consumer appears willing to pay more for beef.
To take advantage of this opportunity, it’s important to know the basics that make corn silage a viable and functional option in your feed ration.
Nutritional value of modern corn silage
Today’s corn silage is approximately 50 percent corn and 50 percent forage. Adding 20 to 40 percent corn silage on a dry matter (DM) basis provides 10 to 20 percent roughage and 10 to 20 percent grain.
Depending on local feed availability, costs and performance goals, you can supply 50 to 90 percent of your feed needs for growing calves with just two feed ingredients: corn silage and processed corn or distillers grains. (To adjust to corn silage, newly weaned calves will need an adaptation period, during which the calves will develop an appetite for new feeds and their rumen bacteria will adjust.)
With proper harvest, storage and feedout management, dry matter shrink can be minimized and nutritional value can be maximized, resulting in more economically efficient and productive feeding performance.
Silage maturity affects nutritional value
Corn silage harvest maturity has a dramatic impact on the nutritional value of individual hybrids. Corn silage is a grass plant containing digestible fiber combined with high-moisture corn.
The increased starch content as the plant matures is responsible for most of the quality improvement, with minimal effect on reducing fiber digestibility in hybrids with excellent late-season plant health.
Adjusting for dry matter content
Cattle performance is based on dry matter intakes and nutrients, and should always be formulated on a dry matter basis to align with the reporting of nutrient requirements for beef cattle.
After formulation on a dry matter basis, values can be converted to an as-is basis (using the moisture content of the feed) to determine the actual amount that should be fed.
If you are a beef producer contracting silage from a grower, it is important for both of you to agree on a base moisture level in your purchase agreement. See Figure 1 for an example.
Importance of correct moisture – too wet or immature
Harvesting corn silage prematurely reduces yield per acre and starch deposition, resulting in an unrealized economic loss.
Corn silage harvested at moistures levels above 70 percent will not only yield less but may result in seepage and undesirable clostridial fermentation.
Clostridia bacteria are inefficient and convert forage sugars and organic acids into butyric acid, carbon dioxide and ammonia.
The silage may have high levels of foul-smelling butyric acid with a higher pH, high dry matter losses and poor feed quality, palatability and intake potential.
The corn plant will approach silage harvest maturity about 35 to 45 days (approximately 900 GDUs) after silking. Most of the variance between hybrids of different relative maturities is the length of time between emergence and silking, not from silking to harvest.
The 35-day to 45-day post-silking recommendation targets 30 to 38 percent whole-plant dry matter.
Importance of correct moisture – too dry
Packing bunkers and piles is one of the most critical elements in ensuring quality silage. Poorly packed, low dry-matter corn silage will have an extended plant cell respiration, resulting in an increased loss of digestible nutrients.
Entrapped air can allow the growth of aerobic micro-organisms (harmful yeasts and molds) which are detrimental to the ensiling process.
When re-exposed to air, yeasts already in the silage can grow and use lactate. This reduces the feeding value by generating heat and volatilization of readily digestible nutrients and energy.
Density is what is measured at the bunker, but it is really porosity (trapped air plus air movement) that management approaches are trying to reduce. The goal is to target porosity values less than 40 percent, ultimately reducing trapped oxygen and oxygen penetration into the exposed face.
Proactive management of optimal silage maturity – on-farm field testing
Growers need to ensure the corn crop is at the optimal silage maturity and moisture before the silage is harvested. In addition to monitoring the silking date, growers can monitor the kernel milk line.
This is done by breaking a cob in half and looking at the kernels from the top half of the ear. After denting, a whitish line can be observed on the kernels. This line is where the solid and liquid parts of the kernel are separated while maturing and drying and will progress from the outer edge of the kernel toward the cob.
The traditional recommendation has been to harvest when the milk line is between one-half and two-thirds of the way to the cob. However, there is considerable variation in the percent kernel milk line and the moisture percent of the whole plant.
University of Wisconsin data over many years show a range in whole-plant moisture at one-half milk line of 52 to 72 percent, with an average of 63 percent. Current recommendations are to target a minimum of three-quarters kernel milk line and whole-plant DM closer to 32 to 38 percent, with newer genetics possessing agronomic and technology traits that confer improved late-season plant health. 
For a detailed assessment of on-farm moisture measurement techniques based on studies conducted by the UW Soil & Forage Analysis Lab at Marshfield, WI, go to “On-Farm Moisture Testing of Corn Silage” by John Peters.
References omitted due to space but are available upon request. Click here to email an editor.
- Bill Ramsey
- Western Livestock Information Manager
- DuPont Pioneer
