Forage crops harvested for silage naturally contain both “good” and “bad” microorganisms. “Good” microorganisms include lactic acid producing bacteria (LAB) that help ensile the crop. “Bad” or spoilage microorganisms include clostridia, enterobacteria, bacilli, yeast and molds that negatively affect silage quality.
Forage inoculants contain live bacteria and are sometimes combined with enzymes. The bacteria are applied to inoculate freshly harvested forage with “good” microorganisms. Enzymes, when present, improve fiber digestibility and increase the soluble sugar content for the “good” bacteria.
Inoculants are primarily used to:
- Stimulate or ensure a rapid, efficient fermentation
- Inhibit aerobic spoilage
Benefits of Forage Inoculants
Incorporating an inoculant into your ensiling program can help:
- Optimize feed value. Using inoculants allows the forage to reach a pH level where protein-degrading bacteria are inhibited rapidly. This results in improved protein retention in grass silage.
- Optimize intake. Inoculants limit production of unpalatable elements, such as biogenic amines.
- Improve safety. Listeria and butyric spores are sensitive to a low pH. With a rapid acidification, there is less opportunity for these microorganisms to develop.
- Reduce losses. Inoculants containing both homo- and heterofermentative lactic acid bacteria reduce dry matter (DM) loss by accelerating the acidification process. Thy also produce anti-fungicidal properties, which reduce losses caused by yeasts and molds as well as heating at the silage face after opening.
Bacterial forage inoculants generally contain efficient (homofermentative) LAB such as Lactobacillus plantarum, Pediococcus acidilactici or Pediococcus pentosaceus. These LAB help increase the rate of pH drop and decrease the production of acetic and butyric acids.
Inoculants designed to inhibit spoilage may contain specific LAB — for example heterofermentative bacteria such as Lactobacillus buchneri — or propionic-acid-producing bacteria. These products are designed for use on materials more prone to aerobic spoilage such as grass (>30% DM), corn, cereal silages, high moisture corn (HMC), cereal grains and baleage.
Strains of Bacteria
Not all bacteria are the same — even if they have the same name. Companies have unique strains that have been tested and developed under rigorous conditions. Bacterial strains need to be proven for use on forage. Look for strain identification numbers and make sure they match up with those used in trials.
Other Fermentation Aids
Bacterial forage inoculants are one type of fermentation aid, or fermentation stimulant. In general, bacterial forage inoculants provide a more predictable outcome than other fermentation aids, such as:
- Sugars: Adding sugars, such as molasses, can improve fermentation in some forages. However, molasses application can worsen effluent losses. In addition, the high rate of application and viscosity make it more difficult to apply than other additives.
- Byproducts: Citrus pulp or pineapple pulp can be used a fermentation aid. However, these products are only available seasonally and to a limited number of producers.