Quality silage is a critical component for many dairy operations. The industry has long recognized how valuable high-quality forage, in general, is in the diet of dairy animals, particularly lactating cows.

A great deal of work has been done to identify and develop methods, programs and products that will work toward ensuring forages of significant nutritional value.

One of the common tools used in producing quality silage is the use of an inoculant. Interestingly, even though inoculants have been used for years, a great deal of confusion and poor information still exists concerning this group of products.

A little review

In general, inoculants are bacterial products that, when added to freshly chopped forage, break down naturally occurring carbohydrates (mainly sugars) to produce organic acids which help reduce the overall pH of the forage material. Silage inoculants work by shifting silage fermentation toward better crop preservation.

That happens when lactic-acid bacteria in the inoculant overwhelm the natural lactic-acid bacteria on the crop. However, even the best inoculants are not always successful.

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Homo-fermenters vs. hetero-fermenters

The two main types of silage inoculants include traditional homo-fermenters, such as Lactobacillus plantarum, Pediococcus species and Enterococcus faecium, and more recently the hetero-fermentative bacteria Lactobacillus buchneri. Homo-fermenters convert six-carbon sugars into one product: lactic acid. In contrast, hetero-fermenters produce multiple products.

For example, they may convert six-carbon sugar into lactic acid, acetic acid and carbon dioxide; or lactic acid, carbon dioxide and ethanol; or convert lactic acid into acetic acid and carbon dioxide.

Key attributes of these fermentation products are:

  • Lactic acid is a strong acid, weak spoilage inhibitor and is fermented by rumen bacteria.

  • Acetic acid is a weak acid, good spoilage inhibitor and unfermented in the rumen.

  • Ethanol is neutral, a poor spoilage inhibitor and partially fermented in the rumen.

  • Carbon dioxide is lost dry matter.

Thus, the best inoculant depends on your goals. If preserving crop quality is your primary goal, use a homo-fermenter that maximizes lactic acid production. If minimizing heating is your primary goal, use a hetero-fermenter (L. buchneri) that produces acetic acid.

Homo-fermenter research

Homo-fermentative inoculants have often lowered silage pH – but not always – and they’ve lowered pH in hay crop silages more often than whole-grain silages. Lowered pH was achieved 58 percent of the time with alfalfa trials, 63 percent with grass silages, 43 percent with corn silages and 31 percent with small-grain silage trials. Dry matter recovery was improved by about 6 percent in 38 percent of trials or by 2 to 3 percent averaged overall trials.

On average, 3 to 5 percent increases in intake occurred in 27 percent of research trials, weight gain in 52 percent and milk production in 46 percent of research trials. Bunk life/aerobic stability were improved in 28 percent of trials but reduced in 31 percent of trials; changes were generally positive in hay crop silages and negative in corn silage and small-grain silages but small, regardless.

Hetero-fermenter research

A recent solution to bunk life issues with whole-grain silages is the hetero-fermentative L. buchneri. Lab studies with L. buchneri have increased acetic acid and slightly increased pH. Since acetic acid inhibits yeasts and molds, L. buchneri-treated silages have been more aerobically stable than untreated silage.

Silages inoculated with L. buchneri have been intermediate in dry matter recovery compared to untreated silage and homo-fermentative-treated silage, since carbon dioxide is made or lost when acetic acid is produced. In lactation trials with L. buchneri-treated silage, bunk life and aerobic stability have increased consistently.

Acetic acid has also increased consistently, more than 5 percent in several cases. However, dry matter intake and milk production by cows has been unaffected by these inoculants.

Combined research

Several small-scale studies have results consistent with L. buchneri for aerobic stability, fermentation products and pH. Cow trials are in progress.

When are inoculants useful?

Positive results are most likely when homo-fermentative inoculants are applied to hay crop silage with wilting times of less than or equal to one day, and when corn silage is harvested dry (e.g., after a killing frost). Based on limited research, L. buchneri inoculants work across a wide range of conditions.

Wet or dry inoculants?

Bacterial inoculants work only if the bacteria are alive when they’re applied, so store them in a cool, dry place. Don’t use chlorinated water to dilute wet inoculants unless the chlorine level is less than 1 part per million, or the inoculant contains chemicals to take care of the chlorine, as chlorine can’t discriminate between “bad” and “good” bacteria.

Choose a wet or dry inoculant based on how well you can keep it alive before and while applying, and how well you can mix it with the crop.

Summary points

Homo-fermentative inoculants are best to improve dry matter recovery and animal performance, particularly with hay crop silages. For bunk life or aerobic-stability problems, is it due to a management issue that can be solved without an additive?

If not, L. buchneri is a good alternative to propionic acid or anhydrous ammonia, as it’s safer to handle, cost-competitive and has similar effects on dry matter recovery and animal performance. L. buchneri is 85 percent effective on corn silage but a slow grower that requires 45 to 60 days of storage to be effective, so it’s ineffective for heating problems with immature silage.  end mark

ILLUSTRATION: Illustration by Kristen Phillips

You can email Dr. Steve Blezinger or call (903) 352-3475. Follow him on Facebook. 

Steve Blezinger