Silage inoculants are bacteria that are used to manipulate and enhance fermentation. Until recently, most inoculants have been homofermentative strains of lactic acid producing bacteria (LAB). The primary benefits of LAB inoculants are a more efficient fermentation, resulting in improved dry matter recovery and improved animal performance. The recent introduction of corn silage inoculants containing heterofermentative strains of Lactobacillus buchneri is quite different because they also produce acetic acid. This reduces the growth of yeasts and makes the silage more resistant to spoilage and heating at feed out and improves silage bunk life.
Aerobic Stability Increases Bunk Life
Lactic acid bacteria increase the fermentation rate, causing the pH to decline faster and lower. By using a LAB inoculant products of fermentation are shifted, resulting in more lactic acid and less acetic acid, ethanol and carbon dioxide. However, lactic acid can easily be metabolized by yeasts and molds in the presence of oxygen. Conventional LAB inoculants that reduce acetic acid can actually reduce bunk life, but this is partially offset by the reduced pH, particularly in haylage. On the other hand, acetic acid can inhibit the growth of various yeasts that are responsible for heating when exposed to oxygen.
Research at the USDA Forage Research Center in Wisconsin and at the University of Delaware has shown that the inoculation of corn silage with L. buchneri can reduce yeast and mold growth at feed out. L. buchneri utilize lactic acid to produce acetic and propionic acids. Stability is improved, with silage temperatures not increasing as readily upon exposure to air. Simply put, corn silage stayed fresher longer. To date, research studies have shown that L. buchneri treated corn silage with higher acetic acid levels does not reduce feed intake.
Fermentation Losses Versus Aerobic Spoilage
The increased acetic acid and aerobic (exposed to air) stability comes at the expense of increased fermentation dry matter losses. However, dry matter losses due to aerobic spoilage of corn silage are typically much larger than fermentation losses. In situations where spoilage at feedout is an issue, the use of L. buchneri inoculant on corn silage may result in less mold and mycotoxins, improved palatability and intake, and reduced total dry matter losses.
When To Use Buchneri Inoculants
L. buchneri inoculants should be considered in situations where aerobic stability is a greater risk. Although L. buchneri inoculants could work similarly with alfalfa and grass haylages, aerobic stability is more of a problem with silages that contain large amounts of starch, such as cereal silage and corn silage. High dry matter corn silages, and bunk, pile or pit silos with large exposed surfaces usually have greater problems with aerobic stability and may benefit more from L. buchneri inoculants. The same may be true for the top loads in either vertical or horizontal silos. In tower silos, it is usually the bottom of silo that is fed during the warmer summer temperatures, when there is increased risk of aerobic spoilage.
Another application where L. buchneri inoculants may be a benefit is in situations where corn silage is expected to be transferred from one silo to another. L. buchneri inoculants have also been shown to increase aerobic stability in high moisture corn. Remember that aerobic stability is also improved by proper silage management practices, including recommended moisture and chop length, rapid filling and packing, sealing, face management, removal rate and feed bunk management.
Commercially Available Products
There are many strains of L. buchneri and they are not all necessarily equally effective. Commercially available L. buchneri inoculant products include Pioneer brand 11A44 (strain 202118) and Biotal Buchneri 40788. Be sure to follow label recommendations.
For information on haylage inoculants, refer to "Haylage Inoculants" on the OMAF Forage Website at www.gov.on.ca/OMAF/english/crops/field/forages.html.