Forages: Harvest & Storage- Haylage & Corn Silage

Excerpt from Agronomy Guide for Field Crops (Chapter 5)

Order OMAFRA Publication 811: Agronomy Guide for Field Crops

Table of Contents

1. Introduction
2. Silage Crop Storage Types
3. When to Harvest Corn Silage
4. Silage Fermentation
5. Silage Storage Losses
6. Recommended Haylage and Corn Silage Management Practices
7. Silage Bacterial Inoculants
8. Common Silage Problems and Causes
9. Silo Gas
10. Large-Bale Haylage
11. Updates on Forages: Harvest & Storage - Haylage & Corn Silage
12. Related links...

Introduction

Storing forage as hay-crop silage, or haylage, has advantages over storing it as hay. These advantages include:

• lower harvest losses
• lower labour costs because all operations can be mechanized
• less dependence on good drying conditions, which allows the crop to be cut at the desired maturity.

Corn silage is a popular forage crop due to palatability, high-energy density and single harvest convenience.

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Silage Crop Storage Types

The most common types of silage storage are:

• vertical (tower) silos
  • conventional open top
  • oxygen limiting (sealed)
• horizontal silos
  • bunker
  • piles
• silage bags
• large bale haylage

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When to Harvest Corn Silage

Harvesting corn silage at the correct moisture is critical for feed quality. The best livestock performance and corn silage fermentation usually occur when whole plant moisture is 65%-70%. This corresponds well to horizontal and bag silos, but silage may have to be somewhat drier in tall tower silos to prevent seepage. Refer to the recommended moistures.

Kernel Milk Line

The kernel "milk line" is often used to determine when to harvest corn silage. This is done by breaking a cob in half and looking at the kernels. After denting (0% milk line), a whitish line can be seen on the kernels. This line is where the solid and liquid parts of the kernel are separated while maturing and drying. This line will progress from the tip to the base. When it reaches the base (100% milk line), a black layer will occur. The traditional recommendation has been to harvest from one-half to two-thirds milk line.

There is considerable variation in the percentage kernel milk line and the moisture percentage of the whole plant. Whole plant moisture at one-half milk line has a wide range in percentage moistures that may be too wet for some and much too dry for others. When the weather is relatively dry, the whole plant moisture may be lower than expected at any given milk line position. There are also hybrid differences in kernel milk line, due to the "stay-green" characteristic. A high stay-green rating means there is faster grain dry-down relative to stover dry-down. This is desirable in a grain hybrid, because as the grain dries, the stalk stays green and healthy, and broken stalks and lodging in late season are less likely. Many silage-only hybrids have a low stay-green rating, so the grain will have higher moisture relative to the whole plant. Lodging is less important in silage and having more moisture in the grain portion increases starch digestibility. Hybrids with high stay-green ratings may have milk lines that are more advanced relative to whole plant moistures. Silage-only hybrids that have lower stay-green ratings will be ready to harvest at a less advanced milk line. Check with your seed company representative for historic milk line recommendations for a given hybrid.

Measure Percent Moisture

Because of the variation between milk line and whole plant percent moisture, the most accurate method of determining when to harvest is to measure the moisture content. Sample at least 10 plants from the field, avoiding the headlands. Watch for moisture variability within fields. Chop a sample using a harvester or yard chipper. Use a commercial forage moisture tester, microwave or laboratory to determine the percentage of dry matter. Moisture testers and microwaves may not remove all the residual moisture in the sample and may underestimate moisture by about 3%. The finer the sample is chopped, the easier it will be to dry and the more accurate the result.

Shortly after denting, when the milk line is about 20%, a whole plant moisture can be determined. In a typical year, corn silage at this stage dries approximately 0.5% per day. Therefore if the sample was 70% moisture, and 65% moisture is the target, harvest should be done about 10 days after the corn was sampled. In dry years, the drying rate will be more rapid; in wetter years, the drying rate will be slower. Moistures can be checked again closer to harvest if necessary.

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Silage Fermentation

When forage is first put into a silo, conditions are aerobic (oxygen is present in the silage mass). Aerobic bacteria produce some heat as they break down carbohydrates and sugars into carbon dioxide and water and use up the trapped oxygen.

When the oxygen has been consumed, the silage becomes anaerobic, which promotes the growth of anaerobic bacteria. These organisms convert the carbohydrates and sugars to organic acids that preserve the silage. In addition, some of the protein is broken down into amino acids, ammonia and other non-protein nitrogen compounds. During this ensiling process, the acids lower the pH, while the production of ammonia tends to raise it. The production of ammonia increases the amount of time it takes to reach a stable pH.

In 2 or 3 weeks, the silage reaches a stable pH of 4.0 to 5.0, and all bacterial and enzymatic activity stops. Once this stable pH has been reached, further breakdown of nutrients and spoilage is prevented, and the silage will keep for extended periods of time, provided air is excluded.

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Silage Storage Losses

Most silage storage losses are associated with exposure to oxygen.

Respiration Losses

When plants are harvested and ensiled, the plant cell respiration continues, resulting in a breakdown of sugars and other carbohydrates.

Fermentation Losses

Primary and secondary fermentation result in varying amounts of fermentation losses. An extended period of fermentation can result in an excessive breakdown of sugars. Some types of bacteria are less efficient than others. At moistures over 70%, a clostridia fermentation can occur, which is very inefficient and produces high levels of butyric acid.

Seepage Losses

When excessively wet material is put into a silo, the weight of the material can squeeze moisture from the silage at the bottom. The seepage carries sugars and other nutrients out of the silo. In addition, seepage can lead to excessive corrosion of the silo walls, reinforcing rods and the possible collapse of the silo. Silo seepage is also harmful to the environment. Refer to the OMAFRA Factsheet How to Handle Seepage From Farm Silos, or visit the Web site at www.omafra.gov.on.ca/english/crops.

Heating

Heating causes plant sugars and proteins to combine and form indigestible compounds. This results in a "toasting" or browning of the silage and reduced protein digestibility. In extreme cases, because the silage is too dry or a continuous supply of air is getting into the silage, spontaneous combustion can lead to a fire. Such fires can happen at any time of the year and are almost impossible to extinguish.

Surface Spoilage

Less compacted, uncovered silage spoils because continuous exposure to oxygen results in the growth of aerobic microorganisms (yeast, moulds and aerobic bacteria).

Feed-Out Losses

When a silo is opened to remove feed, there can be further losses in feed value. These losses are caused by moulds and yeast that become active in the silage when it is again exposed to oxygen. Secondary losses can occur at the cut face of the silage mass or in the bunk while being fed.

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Recommended Haylage and Corn Silage Management Practices

1. Store at Correct Moisture Content
   • conventional upright silos: 60%-65%
   • horizontal silos: 60%-70%
   • oxygen-limiting silos: 50%-60%
   • bag silos: 60%-70%
   • wrapped large bale haylage: 40%-60%.

   Silage that is too dry will result in poor packing and air exclusion, poor fermentation and the production of heat. If haylage becomes too dry, cut fresh material and continue to fill the silo by alternating fresh and dry loads. The addition of water will not increase the moisture of dry silage. The water is not absorbed by the silage and can easily run off; a garden hose does not deliver enough water to make an appreciable difference in moisture content. Silage harvested at moisture percentages greater than 70% can result in seepage and an undesirable clostridia fermentation that results in butyric acid formation, high dry matter losses and poor feed quality, palatability and intake potential.

2. Use Proper Length of Cut

   Fine chopping helps to exclude air by allowing tighter packing but needs to be compromised with rumen function requirements. The actual particle length will be different from the theoretical length of cut (TLC) and can be checked with a particle length separator.

   With haylage, a 10-mm (7/16-in.) TLC is usually desirable. Low moisture silage may require a shorter TLC (6 mm or 1/4 in.) to ensure adequate packing. The length of cut is probably more critical with horizontal silos, although it is still important with upright and sealed silos. Harvester blades must be sharp and correctly set. Chopping finer than 6 mm (1/4 in.) is not recommended as it doesn't improve packing but does require more horsepower and may result in nutritional problems.

   Corn silage harvest processors use rollers attached to the chopper to break cobs, crack kernels and shred stalks. The TLC recommended with processors is 19 mm (3/4 in.) rather than 10 mm (7/16 in.) without a processor. Processors may be more beneficial with relatively dry, hard-kernel, textured corn.

3. Fill Silos Rapidly

   Fill as quickly as possible to speed fermentation and minimize spoilage. If filling is delayed for a few days, the silage should be covered with plastic to reduce the chance of spoilage. In an upright silo, the silage is not compacted until a considerable depth of material has been put in the silo. The top part of the silage will be less dense and hold more air that could cause heating and loss of quality.

4. Pack Horizontal Silos Well

   Bunk silos should be filled from back to front so that a "progressive wedge" shape is created, rather than filling from bottom to top. As the silo is filled, it should be packed in relatively thin layers (15 cm or 6 in.) to obtain good air exclusion. Sufficient tractor weight and packing time are critical. This may mean adding more packing tractors or reducing the delivery rate of silage to the bunker to increase packing time per tonne.

5. Provide a Tight Tower Silo

   A tower silo can act as a chimney. If air can get in, it will move up through the silage mass, which could lead to spoilage, heating of the silage and, in extreme cases, fire. Cracks in the silo walls or around the doors should be caulked or reconditioned to prevent the entry of air.

6. Distribute Silage Evenly Within Tower Silos

   Without good distribution, the lighter material will collect along the wall, thereby leading to poor packing.

7. Seal Silos Well
   • Covering and sealing with plastic is essential in horizontal silos. The plastic should be held firmly in place. Old tires placed closely together (touching) work very well. The plastic should not be allowed to flap in the wind, because it then acts as a bellows and pumps air into the silage rather than excluding it.
   • In conventional tower silos, forage at the top has low density that air can penetrate. To reduce spoilage until fermentation is complete, silage should be covered with plastic and weighted down by a few centimetres of silage. Take silo gas precautions. (See the section Silo Gas.)
   • In sealed silos, the hatches should be closed at night and during interruptions in filling. When filling is complete, the hatches should be closed immediately.
8. Allow Complete Fermentation

   Silage fermentation requires up to 21 days. To ensure silage stability and maximize feed bunk life, do not feed out of the silo until this is complete.

9. Feed Out Quickly to Minimize Spoilage

   The removal rate will determine the amount of spoilage at the face of the silage. Silos should be sized accordingly. Tower silos should be emptied at a rate of at least 5 cm (2 in.) per day in winter and 7-10 cm (23/4-4 in.) per day in summer. Horizontal silos should be fed out at a minimum rate of 10-15 cm (4-6 in.) per day, depending on the season.

10. Silage Face Management to Minimize Spoilage

    Silage should be removed from horizontal silos by scraping the silage face from top to bottom with the loader bucket. Removing silage by lifting the bucket from the bottom to the top disrupts the pile and allows oxygen to penetrate and initiate aerobic spoilage. Shear buckets that minimize silo face spoilage are also commercially available.

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Silage Bacterial Inoculants

Silage inoculants are additives containing lactic acid bacteria (LAB) that can enhance fermentation. The LAB increases the rate and efficiency of fermentation, causing the pH to decline faster. The primary benefit is decreased dry matter losses. Protein solubilization can be reduced slightly. Animal performance and feed efficiency can be improved. Bunk life may or may not be improved, depending on the pH and acetic acid levels.

Bacterial silage inoculants usually contain Lactobacillus plantarum and other bacteria species. The product should supply at least 100,000 live bacteria cfus (colony-forming units) per gram of forage when applied at the recommended rates. Liquid products may have some advantage over dry products because of more uniform application.

If there is a high natural population of lactic acid bacteria, an inoculant is less likely to provide a benefit. The natural population is increased by higher than average wilting temperatures, longer wilting times, rain during wilting and higher moisture contents during chopping. Inoculants are usually less beneficial in corn silage than in haylage.

The application of a silage inoculant will not overcome the effects of poor silage management or poor weather conditions. These products are most effective when applied to top quality forage under top management.

Forage additives, including silage inoculants, must be registered with the Canadian Food Inspection Agency (CFIA) to be sold in Canada. To receive a "permanent" registration, companies must provide research that substantiates a nutritional label claim. Where research has been conducted but the results are not conclusive, products may be eligible to receive a "temporary" registration for up to 3 years to conduct additional research that substantiates a label claim.

Temporary registration numbers start with a "T." Ask company representatives to provide independent research that substantiates their claims for the product. It is important that the product is labelled for the crop being ensiled, and that directions for storage and use are followed.

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Common Silage Problems and Causes

There are several common problems associated with silage. Table 5-14. Common Silage Problems and Causes, lists potential reasons for these problems.

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Silo Gas

Nitrogen dioxide, NO₂, is a dangerous chemical asphyxiant that is produced as a result of chemical reactions that take place almost immediately after plant material is placed into a silo. Even short-term human exposure can result in sudden death. It has a characteristic bleach-like odour and may be visible as a reddish-brown haze. It is heavier than air, therefore it will tend to be located just above the silage surface. It may also flow down silo chutes and into feed rooms.

Weather conditions and cultural practices will affect the amount of nitrates in plant material, which in turn will set the stage for the production of NO₂ in the silo. For example, a dry period during the growing season followed by abundant rainfall will encourage a corn crop to take up high levels of dissolved nitrates. If the corn is harvested before the nitrates can be converted to proteins, nitrous oxide (N₂O) and nitric oxide (NO) are produced. Unstable NO combines with oxygen to form deadly nitrogen dioxide.

When inhaled, NO₂ dissolves in the moisture on the internal lung surface to produce a strong acid called nitric acid. Nitric acid burns the lung tissues, which is followed by massive bleeding and death. Repeated exposure to lower concentrations of NO₂ will cause chronic respiratory problems, including shortness of breath, coughing and fluid in the lungs. Seek medical attention immediately.

Silo Gas Precautions and Procedures

• Post a "Silo Gas" warning sign in a visible location near the silo.
• Do not allow children or visitors near the silo for 3 weeks after filling.
• Contact your local fire department to determine if pressure-demand remote breathing apparatus is part of their emergency equipment. SCUBA equipment is not suitable because the air tank is too big for climbing the silo chute or the outside ladder-cage.
• Provide sufficient feed room ventilation to exhaust any silo gas that may have spilled from the silo.
• During filling, adjust the distributor as needed to level silage. Do not level material by hand.
• If it is necessary to enter the silo when filling is complete, do so immediately following the last load, on the same day. Leave the blower running while inside the silo.
• Silo entry should not be attempted without wearing a lifeline that is in the hands of sufficient outside help to pull you to safety.
• If it becomes necessary to enter an oxygen-limiting silo, it is essential that an external air supply be worn.
• A top unloader can usually ventilate a silo effectively. However, if it becomes necessary to service a defective unloader, assume that gases are present. To expel gases before entering, run the forage blower with the chute doors closed and the roof vent open. If the head space is greater than 5 m (16 ft), attach a tube adapter to the blower pipe. For a 7.2-m (24-ft) diameter silo with 5-10 m (16-33 ft) of head space, increase the ventilation time. Leave the forage blower running while in the silo.

Refer to the OMAFRA Factsheet Hazardous Gases, or visit the Web site at www.omafra.gov.on.ca/english/crops.

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Large-Bale Haylage

Large-bale haylage, or "baleage" as it is also called, has become popular as an option for storing excellent-quality forage. By making large bales into haylage, a farmer can be more aggressive and consistent in cutting schedules as it reduces the weather risk factor. Some farmers use this as their main storage system, but it is more commonly a flexible second system of storage when silos are full and the weather doesn't permit drying. It produces a long stem haylage. Plastic bagging or plastic wrapping is used.

The system makes use of equipment such as large round balers, which are readily available. Baleage may be fed using the same equipment as dry, large bales. This provides flexibility, to make as little or as much large bale silage as the weather dictates. Heavier equipment and four-wheel-drive tractors may be required when handling the heavier bales.

The cost and disposal of the plastic coverings have been major concerns. Cost is rationalized by considering the higher protein and energy value of the stored forage and the importance of the storage itself. Reduced harvesting losses and the higher quality of the whole forage crop as the harvest is moved ahead should be considered when determining the cost benefit of the system. Refer to the OMAFRA Factsheet Recycling Farm Plastic Films, or visit the Web site at www.omafra.gov.on.ca/english/crops.

With large-bale haylage, there is less or incomplete fermentation resulting in a higher pH, or less acidic environment, and a more unstable silage than conventional haylage. This means that greater emphasis must be put on good silage-making processes, especially the exclusion of oxygen. The length of storage time and how long the bales are exposed to oxygen before feed-out must be adjusted to weather conditions.

Successful use of baleage involves the following management practices:

• Bale a good quality forage within 40%-60% moisture content in a very compact, even bale.
• Avoid contamination by manure use and soil-borne bacteria splashed up with rains or by raking.
• Store the bales quickly, excluding the oxygen as soon as possible. Monitor bales to maintain a continuous seal.
• Ensure efficient, quick feed-out to avoid bunk spoilage.
• Use good-quality plastic to produce a sealed environment.

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Updates on Forages: Harvest & Storage - Haylage & Corn Silage

No updates available at this time.

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Related links...

• Forages

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