When it comes to feeding your livestock, ensuring they receive the best possible diet is crucial. And as any farmer will tell you, silage is a key component of livestock feed.
However, not all silage is created equal. Several factors can affect its quality and nutrient content. In this article, we’ll uncover the four main factors that impact silage quality to ensure your livestock get the best possible feed.
Basics of Silage
Before diving in, it’s important to understand the basics of silage and the science behind how it’s made.
Some of the most common crops grown for silage are corn, sorghum, barley, oats, alfalfa, rye, wheat, triticale and millet. As crops reach maturity, they’re harvested and chopped into small pieces before being stored where anaerobic (without oxygen) bacterial fermentation occurs.
The fermentation process is what makes silage different from hay, as the bacteria on the plant consume carbohydrates (sugar) and produce lactic acid. This brings down the pH level of the pile and preserves nutrients. Once the pH of a pile drops to 4, fermentation is complete. The amount of fermentation and lactic acid produced in a silage pile is determined by these four factors: moisture, compaction, oxygen and fermentation.
1. Moisture: Harvest Timing
Moisture level matters when making high-quality silage. Depending on the crop, maturity, and storage method, moisture levels may vary. Corn silage for a horizontal pile (bunker) should be between 65-70%. Anything above 70%, yield potential is reduced, and seepage will occur which can favor the growth of butyric-acid-producing Clostridia bacteria.
The activity of butyric acid-producing Clostridium increases significantly in higher moisture silage. This has a negative impact on livestock performance often resulting in reduced milk production, diarrhea, ketosis and mastitis. Additionally, it leads to greater dry matter loss.
On the other hand, any moisture below 58% can also pose a risk. With less moisture, silage becomes spongy and doesn’t pack well, trapping oxygen and allowing for aerobic (with oxygen) metabolism, which produces heat and silage fires.
Optimal moisture for your silage pile depends on crop maturity. Corn should be harvested at the mid-dent stage (1/2 milk line) and at 65-70% moisture. Harvesting at the right time ensures the crop has the highest nutrient content while maintaining a good moisture level.
Photo credit: Top crop manager
To create top-notch silage, start by harvesting the appropriate plant at the right moisture level. Chop the plant into small pieces, typically 0.5 to 2 inches long. This smaller size enables bacteria to break down the forage more rapidly and fermentation can begin. And remember, proper compaction and air elimination is crucial for successful fermentation.
2. Compaction: Good for Silage
Filling your silage pile with uniform 6” layers is the best practice for silage production and good compaction. Packing is the most cumbersome step during filling, but it’s the most critical step in the process!
The goal is to achieve an adequate bunker density of at least 14 lbs./cubic foot of silage. To achieve this, it’s essential to have sufficient tractor weight on the pile, at least 1,000 lbs. of tractor weight per ton of silage/hour.
The bunker density is measured after completing the pile. Free calculators are available to help you determine bunker density. The basic bunker calculation is length (ft) x width (ft) x depth (ft) x density (lb./cu-ft) at the final moisture content. Remember, an adequate bunker density helps to limit the air in the pile and reduce dry matter loss caused by bacteria and yeast. Tracking your bunker density year to year is crucial for understanding your progress and improving for future seasons.
Dry matter loss is yet another crucial factor that should be considered during silage compaction. The top of the pile usually has greater dry matter loss than the bottom, due to the natural packing density difference. Studies show that a pile with a 14 lbs./cubic foot average has a density of 16.8 lbs./ft3 on the bottom, but only 9.5 lbs./ft3 on the top which translates to a difference of 6.1% dry matter loss. The denser bottom lost 5.6% dry matter loss, while the top had an 11.7% dry matter loss. This indicates that density has a significant impact on preservation. Therefore, if the silage density is low, expect high dry matter loss which can result in low feed quality and poor animal performance.
3. Oxygen: Seal the Silage
Despite our best efforts at harvesting at the correct moisture and compacting the pile, all efforts can be wasted from a common invisible threat – oxygen.
Oxygen promotes the growth of aerobic (with oxygen) bacteria, which produce heat, consume nutrients and release gases that reduce feed quality. This can lead to spoilage, high dry matter loss and decreased nutritional value for livestock. Air exclusion is the only way to prevent these issues.
Research shows that air can permeate 30-100 cm (11-40 inches) per day from the silage surface, leading to up to 35% dry matter loss due to surface area exposure. One way to prevent this is to ensure your silage storage is sealed thoroughly or covered to exclude air. The efficiency of your silage seal depends on several factors, such as the quality of the covering material and the sealing technique.
Generally, there are four common ways of storing silage: tower silos and silage bunkers, piles and bags. Tower silos rely on a structural design that limits air infiltration through walls and a roof. Silage bunkers, piles and bags, on the other hand, employ an exclusion method that uses an oxygen barrier with plastic film such as tarps or bags. These storage methods require attentive sealing near the edges and corners with tires, soil or sandbags and proper face management.
Sealing the silage as tightly as possible is critical since even tiny holes can lead to air infiltration and spoilage. Lastly, make sure to invest in silage-specific tarps made of UV-resistant polyethylene material that better stand weather and protect silage over a longer period of time.
4. Fermentation: How Long Does Silage Take to Ferment?
As previously stated, fermentation is critical for proper silage preservation as it helps reduce dry matter loss and lock in nutrients. The faster the pH level in the pile decreases, the more nutrients are saved.
The starting pH of chopped corn can differ, but typically hovers around 6.5. Slow fermentation causes more degraded proteins and increases the release of carbon dioxide and nitric oxide gas which can negatively affect animal health. A pH level above 5 can lead to excess growth of molds and yeasts, leaving spores that can be reactivated when the silage storage is opened. These spores can affect the nutrient quality of your silage and, again, the health of your livestock.
To speed up the fermentation process, incorporate specialized bacteria using inoculants to rapidly reduce the pH below 4.5.
The best time to feed your silage depends on its fermentation time and pH level. Reaching a pH of 4 can take anywhere from 10 days to 3 weeks. But keep in mind that this may vary depending on moisture content, type and quality of inoculant used and temperature. Monitor your pH closely and wait for fermentation to be complete before feeding.
Choosing an Inoculant
Silage bacterial inoculants are divided into two categories depending on how they ferment a common plant sugar, glucose. Homofermenters produce just lactic acid and include some species of bacteria like Lactobacillus like Lactobacillus plantarum, Pediococcus species, and Enterococcus species. The other category, heterofermenters produce lactic acid, acetic acid or ethanol and carbon dioxide. Lactobacillus buchneri is the best example of a heterofermenter.
Homofermenters are often preferred for legume-based silages, such as alfalfa or clover, which have high levels of water-soluble carbohydrates. Homofermenters are efficient at converting these carbohydrates to lactic acid, which helps to lower the pH of the silage, reducing the risk of spoilage.
Heterofermenters, on the other hand, are often used for corn silage or grass silage which have a lower level of water-soluble carbohydrates. Heterofermenters produce acetic acid which is a strong inhibitor of mold and yeast growth that causes fermented silage to spoil when re-exposed to oxygen. This is especially important when feeding from large silage piles to high-producing dairy cows.
It’s important to note that the choice between homofermenters and heterofermenters isn’t always black and white. Some silage inoculants are a combination of both. These products are known as “combination inoculants” and are designed to provide the benefits of both types of bacteria.
It’s also important to consider the quality and quantity of bacteria in the product. The colony-forming units (CFU) count indicates how many viable bacterial cells are present. A higher CFU count generally means a more effective product. Additionally, make sure to review the instructions carefully. Some inoculants require refrigeration and special handling to ensure the bacteria colonies stay alive before application.
Save More Silage with Anchor
Improve your silage preservation with Anchor™ for Silage, an advanced inoculant blend powered by Microbial Catalyst® technology that uses a unique encapsulation process. Anchor not only safeguards beneficial bacteria during storage but also boosts their effectiveness in silage. When activated, each inoculant granule rapidly drops pH for improved fermentation.