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Mar 21, 2022

What makes a good silage inoculant?

Mar 21, 2022

Silage inoculants are based on live bacteria which contribute to improving silage acidification and/or aerobic stability depending on the bacteria activities. The inoculant market is growing, with many different products on offer, claiming many benefits and various price ranges.

There are two main types of bacteria used in an inoculant formulation, depending on the desired outcome:

■ Homofermentative lactic acid bacteria (LAB), which convert soluble sugars from the forage into lactic acid, for example, Lactobacillus plantarum or Pediococcus pentosaceus. These bacteria are used to speedup the initial fermentation, helping to quickly reach a safer pH.

■ Heterofermentative bacteria such as Lactobacillus buchneri and Lactobacillus hilgardii which convert soluble plants sugars into lactic and other acids which have a documented antifungal activity (acetic acid or propionic acid). They are effective to improve silage aerobic stability and hence reduce the risks of aerobic spoilage after opening.

According to Professor Limin Kung, PhD, University of Delaware, “Of the heterolactic acid bacteria, only Lactobacillus buchneri 40788 has proven itself (with multiple research publications) to be an effective silage inoculant.”

However, in the same bacteria species (for example L. buchneri), each strain has its own genetic identity and commercial strains are registered with unique strain numbers (for example L. buchneri NCIMB 40788 from Lallemand Animal Nutrition). All documentation should be linked to a particular-strain number. This means that, for example, what has been published for one L. buchneri strain cannot apply to another.

All inoculant formulations are specific. Inoculants can be based on a single strain or associate different strains with complementary activities. For example, homofermentative and heterofermentative bacteria can be combined to improve both acidification and aerobic stability of low sugar, high DM and high nutrient content forages such as lucerne.

There is no rule as to what is the best combination, but the formulation should respond to specific issues related to each type of crop or silage challenge. For example, maize is prone to aerobic instability due to its high sugar and dry matter content. The best option for preservation is to use a proper strain of L. buchneri or L hilgardii documented to improve aerobic stability. On the contrary, grass silages and legumes have a lower sugar and dry matter content.

In this case, acidifying bacteria is necessary to achieve an ideal acidification. Some inoculants combine bacteria with specific enzymes that raise the fibre digestibility and release soluble sugars to enhance the lactic acid and antifungal bacteria metabolism.

Inoculant formulation should be specifically adapted to the ensiling challenge in order to ensure best silage preservation.

Research is key

Professor L. Kung wrote, “An effective silage inoculant will have independent, statistically analysed, and published data supporting its use. Of course, the more supporting data there is, the more credibility a product has. I will take an educated guess and say that no more than 10-15% of the silage inoculants in the marketplace have more than five publications showing that they work.”

It is important to check that there is independent published research related to the inoculant formulation and/or strain(s). Not all companies invest in continuous research and development to document their products.

Professor Kung explains, “Lactobacillus buchneri NCIMB 40788 has become the gold standard to improve aerobic stability, showing consistent results.”

Always check that the scientific and technical references provided with a product refer to the specific strain.

Production is essential

An inoculant’s efficacy relies on the biological activity of live bacteria. Thus, efficacy of the final product relies on the survival of the bacteria, from the manufacturing plant all the way through to the silage pile.

Bacteria viability depends on the strain (its intrinsic quality), as well as the quality of the production process, formulation, and finally, storage conditions including packaging. The production of live bacteria requires expertise and stringent quality controls throughout the process.

Only a few companies possess the capability to produce bacteria and deliver pure, live, stable, and consistent blend of specific bacteria suitable for silage.

Companies that produce their own bacteria and control the whole chain from bacteria fermentation to final product packaging ensure optimal quality and traceability of the product.

When choosing an inoculant, it is important to check the reputation of the primary producer, the product shelf life and the storage conditions.

Importance of formulation and dosage

Not only is the bacteria composition important, but also the dosage and product formulation technology. One can select the best possible bacteria strains, but if the farmer does not end up with the right number of live and active bacteria in the silage, it is useless for them.

Hence, the number and the viability of the bacteria, as well as solubility and ease of application is very important.

Once the product’s scientific documentation and technology has been checked, it is important to check the dose.

All published data are related to a recommended dose of use, which is expressed as CFU (Colony Forming Units) per gram of fresh forage treated or per gram of product.

The CFU represents the number of live and active bacteria. When comparing two products, it is important to compare the final bacteria count, as sometimes this can help explain the price difference.

For example, L. buchneri is effective at 300,000 CFU/g of fresh forage. Certain products could be misleading as giving the overall bacterial count. It is important to check the number of each individual bacteria to make sure the optimal dose is used.

Always compare dose according to final bacteria count in forage.

Dead bacteria are useless

Number of bacteria or CFU in the sachet is one thing, but the number of live bacteria reaching each part of the crop is another. Lallemand’s inoculants are stored as hydro dispersible powder in an aluminium foil sachet.

The bacteria are preserved in a freeze-dried form and the bacteria are revived when mixed in water for application.

However, bacteria viability after dilution is also dependent on the formulation and technology to deliver a high concentration of bacteria that remain in suspension (low sedimentation) to provide homogenous application of live bacteria throughout the silage harvest.

Look for forage inoculants with Formulation technology that helps ensure viability over time.

Technical support

Successful silage making can meet many challenges and requires technical knowledge.

Silage inoculants are not commodity products and to make sure the investment pays-off, ideal practices should be implemented. Providers should accompany their users with strong technical support.

Professor L. Kung wrote on this matter, “Although technical service is not directly related to the effectiveness of a silage inoculant, this should be factored into your decision-making process. Certainly, companies that are willing to assist you in times of need should be highly considered.”

Check that your provider offers expert technical services on-farm.

There are many silage inoculants on the market with different claims and specifications. Before getting bogged down in the detail, check to see that the product contains bacteria, if it doesn’t, it’s an additive of some other type and not a silage inoculant.

A better understanding of the makeup of a silage inoculant, its modes of action and specificities, help make the right decision.