May 29, 2020
If you use the same inoculant year after year, it’s time to rethink your approach. Choosing which type of inoculant to use each season should be based on the dry matter and condition of the forage you are putting up.
There are three basic types of biological microbial inoculants:
Classical homolactic acid bacteria inoculants are designed to speed up fermentation at the front end of the process.The front end is usually the first two to three days but can go as long as two weeks into fermentation, depending on the dry matter of the crop.
“High dry matter crops ferment more slowly than wet crops; but if a homolactic acid inoculant is added during the active front end of fermentation, it should decrease the pH very quickly and make a lot of lactic acid,” said Dr. Limin Kung Jr., professor of dairy nutrition and head of the Silage Fermentation Laboratory at the University of Delaware. “With the anaerobic conditions in the silo, it should stabilize the fermentation so that it will stop when complete. If it ferments too long, it will use up a lot of nutrients and start to lose dry matter. We always want fermentation to be quick, efficient and produce a stable product.”
Heterolactic acid bacteria inoculant includes Lactobacillus buchneri and improves aerobic stability. However, when heterolactic inoculants were launched, many were puzzled by this new bacteria because it works differently.
“Lactobacillus buchneri doesn't drop the pH faster, and it doesn't make more lactic acid; but what it does anaerobically is that it takes moderate amounts of lactate and makes a little bit of acetic acid,” he said. “Acetic acid in silage was concerning to some because it can lower intake. However, research showed the conversion of the moderate amounts of lactate to acetic acid was just enough to inhibit the yeasts, which are primarily responsible for initiating aerobic spoilage. So, it was possible to limit spoilage and not have a negative effect on intake or dry matter recovery.”
Combination homolactic acid and Lactobacillus buchneri inoculants offer the homolactic benefits at the front end and the Lactobacillus buchneri back end benefits to silage, especially for silage stored and fed-out that may have air penetrating into the silage mass, causing spoilage.
When to Use Different Types of Inoculants
With first cutting often occurring amid rainy, wilting conditions, which are not ideal for harvest, forages must frequently be brought in wetter than they should be. For grasses and legumes that are ensiled on the wetter side, meaning less than 30 percent to 32 percent dry matter, a homolactic inoculant is the best option to jumpstart fermentation.
If silages are in the normal dry matter range, between 35 percent to 37 percent dry matter for corn silage or 35 percent to 45 percent dry matter for haylage, consider using a combination inoculant.
As silages get drier, less fermentation occurs, creating a high probability that silage will spoil when it's exposed to air. Exposure to air could occur during storage because of ripped plastic or bunker piles that are not well packed, but it can also occur during feedout.
“Not using a defacer or feeding out too slowly allows more air to penetrate into the silage mass, which stimulates bad yeasts and destabilizes the system, causing it to heat, mold and spoil,” explained Dr. Kung. “In drier silages that don't pack well, they're more prone to have back end problems than front end problems, especially corn silage, but it still makes sense to use a combination inoculant.”
High moisture corn or snaplage, where the silages are extremely dry, offer an opportunity to use a Lactobacillus buchneri inoculant, as the back end of fermentation will be the issue with those types of silages.