Thursday, July 18, 2024
General Agriculture

Silage Conservation for Animal Feeds and Feeding

Silage is the final product when forage of sufficient moisture (> ~50%) is conserved and stored anaerobically (oxygen-free), under conditions that encourage fermentation of sugars to organic acids.

The acidity generated by the organic acids (mainly lactic acid, but also acetic and propionic acids) and the lack of oxygen prevent the development of spoilage microorganisms.

Three of the most critical factors for silage production are (1) rapid removal of air, (2) rapid production of lactic acid that results in a quick lowering of the pH (this is the result of adequate fermentation processes), and (3) rapid feedout once the silo is opened and exposed to air to avoid heating and spoilage.


Phases of silage fermentation

An overview of the four phases of the silage production process. The phases are as follows:

Aerobic: This phase usually lasts for approximately one day. During this period, plant cells and microbes will metabolize sugars and starch in the presence of oxygen, generating heat in the process.

Silage temperature is elevated to about 90°F, and water may be lost (as seepage) because of respiration and compaction.

If anaerobic conditions are not achieved quickly, high temperatures (>120°F) and prolonged heating will occur due to the growth of unwanted aerobic bacteria, yeast, and molds that compete with beneficial bacteria for substrate.

Therefore, it is critical to ensure good compaction, proper moisture, and good sealing, all of which lead to a rapid transition to anaerobic conditions.

Fermentation: Once anaerobic conditions are achieved, lactic acid bacteria and other anaerobes start to ferment sugars into lactic acid, mainly, and other organic acids to a lesser extent (such as acetic and propionic) that will drop the silage pH from about 6.0 to a range of 3.8 – 5.

Alcohols such as ethanol will be generated too, but with no contribution to the acidification process.

Silage Conservation for Animal Feeds and Feeding

Rapid decrease in pH prevents breakdown of plant proteins and helps inhibit growth of spoilage microbes. Consequently, lactic acid production is preferred to ensure a low silo shrink. The fermentation phase usually lasts from one week to more than a month, depending on crop and ensiling conditions.

Stable:As long as anaerobic conditions are maintained, silage can be stable for months and up to years.

However, under practical conditions, silage should be used within a year of its production. Slow entry of air through areas that were not properly sealed can slowly deteriorate material, thus silos should be constantly checked and maintained to avoid any potential break of seal integrity.

Feedout: Once a silo or bale is opened, it should be used as quickly as possible to avoid aerobic deterioration of the material. When oxygen becomes available in the ensiled material, yeasts metabolize the organic acids, which in turn cause the pH to increase, and further restarts the aerobic activity (such as molds), causing greater silage spoilage.

The design of a typical silo face should allow for the daily removal of approximately 6 inches of face material (for reference, each 6-inch daily removal is equivalent to one week of exposure to air).

Silo opening should occur only after the fermentation phase has been completed (that is, after three to six weeks). The suggested approach is to wait approximately two to three months before opening a silo.

Differences between Silage and Haylage

The main difference between silage and hayage is the initial dry matter (DM) concentration level at which the forage is clipped and packed to achieve optimum anaerobic and fermentation conditions. Three different moisture levels can be achieved: high-moisture silage (≤ 30% DM), medium-moisture silage (30% to 40% DM), and low-moisture (wilted) silage (40% to 60% DM).

Low-moisture silage is referred to as haylage. When baled and wrapped, haylage is referred to as baleage. High-moisture silages are more prone to potential seepage losses (that is, effluent or leachate from the silo), undesirable secondary fermentation (resulting in butyric acid, which results in a rancid smell), and high dry matter losses (silo shrink).

On the other hand, preservation as haylage depends more on achieving adequate packing (high density) to maintain anaerobic conditions.

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Achieving high density at packing is more difficult in drier forage. Nevertheless, high density is critical in haylage to maintain anaerobic conditions because microbes are less active and fermentation is lower in haylage than in higher moisture silage.

Management Practices for Making Better Silage

Crop factors

An ideal crop to be ensiled should have an adequate level of sugars (measured as water-soluble carbohydrates) to be fermented, low buffering capacity (that is, the resistance to changes in pH), and a stand with a dry matter concentration above 20% (McDonald et al., 1991).


Moisture concentration affects the rate and extent of fermentation. Forages should not be ensiled with more than 70% moisture (or less than 30% DM concentration) due to potential seepage losses and growth of undesirable bacteria (such as clostridia), which results in undesirable fermentation. Wilting is needed in most cases when ensiling grasses and legumes.

Particle size

The optimal particle chop length is a balance between the particle size needed to achieve good compaction in the silo and the effective fiber requirements of ruminant livestock, especially lactating animals.

The recommended theoretical length of cut (TLC) is 3/8 to 1/2 inch for unprocessed corn and legume silages, and 3/4 inch for kernel-processed corn silage (Muck and Kung, 2007).

Sorghum silage should have a similar TLC to corn silage and grasses, and cereal silages should have a similar TLC to legume silages. Kernel processing is highly recommended when making corn silage to improve starch digestibility.

Kernel processing should not be done, however, if whole plant DM concentration is less than 30% due to risk of increased seepage losses.

Packing density

Attaining a high density in a silo is important because it determines the porosity at which air moves into the silo and subsequently the amount of spoilage that occurs during storage and feedout. Silage density is influenced by DM concentration, TLC, and packing intensity.


Good sealing with plastic sheets and concrete barriers will keep the carbon dioxide in and prevent oxygen from entering the silo. Care must be taken to seal any holes with UV-resistant tapes, especially in low-moisture silages where porosity is greater.


Several types of additives are available that can be used for silage making. Additives can help in every phase of silage making. Nevertheless, good harvesting practices are the main drivers of silage quality.

In general, additives can be classified as stimulants or inhibitors of fermentation, and nutrient sources (Kung et al., 2003). Specific effects of additives include the following:

Provide fermentable carbohydrates.

Inhibit undesirable types of bacteria and promote desirable bacteria.

Furnish additional acids (such as propionic acid) directly to decrease pH.

Modify moisture.

Extend aerobic stability during feed out (bunk life).

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Benadine Nonye is an agricultural consultant and a writer with several years of professional experience in the agriculture industry. - National Diploma in Agricultural Technology - Bachelor's Degree in Agricultural Science - Master's Degree in Science Education - PhD Student in Agricultural Economics and Environmental Policy... Visit My Websites On: 1. - Your Comprehensive Practical Agricultural Knowledge and Farmer’s Guide Website! 2. - For Effective Environmental Management through Proper Waste Management and Recycling Practices! Join Me On: Twitter: @benadinenonye - Instagram: benadinenonye - LinkedIn: benadinenonye - YouTube: Agric4Profits TV and WealthInWastes TV - Pinterest: BenadineNonye4u - Facebook: BenadineNonye

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