Propionic Acid Can Preserve Wet Corn

Organic acids can help protect harvested high-moisture corn from heating and mold growth.

Published on: Dec 9, 2009
"In situations where fermentation of high-moisture corn is in jeopardy, treatment with organic acids can prevent heating and mold growth," advises North Dakota State University Extension Service dairy specialist J.W. Schroeder. "Organic acids also can be used to preserve high-moisture corn when adequate storage space is not available"

Livestock fed high-moisture corn treated with organic acids perform similarly to animals fed untreated high-moisture corn, he says.

"Keep in mind that propionic acid will not lessen any problems from the mold, but it likely will prevent mold problems from getting worse," Schroeder says.

What kind of organic acid should be used depends on the situation. Organic acids come in two basic forms: pure acid or buffered acids. Pure acids include propionic acid, acetic acid, citric acid and benzoic acid. Buffered organic acids include calcium and sodium salts of propionic, acetic, citric and benzoic acids. Organic acids also can be buffered with ammonia, resulting in the ammonium salts of propionic and acetic acids. Buffered organic acids come in dry or liquid formulations. Buffered organic acids are safer to handle and less caustic to machinery.

When choosing an organic acid, select a product that predominately is made up of propionic acid and has a high percent of active ingredient. In general, liquid products are preferred because they can be applied more evenly.

The rate of organic acid to use is more complicated. The recommended application rate for propionic acid generally has been 12 to 15 pounds per ton, but that might not be the best, according to Schroeder. Producers usually have two philosophies of organic acid application for high-moisture corn preservation.

The first philosophy is using organic acid for full preservation. Preserving high-moisture corn effectively for one year requires 10 to 20 pounds of organic acid, with the acid as the active ingredient, per ton of corn.

A second philosophy is to apply organic acids at low rates of 2 to 5 pounds per ton of high-moisture corn. These low application rates are intended to aid in aerobic stability of high-moisture corn at feedout.

The theory of this practice is to control yeast populations. Normal high-moisture corn fermentation results in the production of lactic acid. At feedout, some yeast species can assimilate (eat) lactic acid and cause high-moisture corn to heat and mold. Yeast cannot assimilate propionic acid. Therefore, applying low rates of propionic acid will stabilize high-moisture corn at feedout by controlling the buildup of yeast populations.

Remember that low application rates of organic acids do not provide full preservation, and high-quality high-moisture corn still is dependent on normal fermentation. Therefore, when using low organic acid rates, the recommendation is to use an inoculant specifically developed for high-moisture corn at ensiling time to help ensure adequate fermentation of the high-moisture corn.

However, fermentation seems unlikely with winter on the way, so inoculants probably won't help much this time of year, Schroeder says.

 If the weather stays cold, which is likely, and the corn is not too wet (28 percent to 30 percent kernel moisture), the corn should be safe to store for the next few months.

"The weather is the wild card," Schroeder says. "If it gets warm, the grain mass will heat quickly and spoil. The weather has been anything but 'normal' this year."

He recommends producers monitor their corn storage bags for holes weekly and patch any damage immediately. They also should plan to use the wet bag-stored grain quickly, preferably before spring.

To determine if fermentation did take place, check the stored corn's pH (alkalinity or acidity). If the pH is in the 3 to 4 range, fermentation took place; if the pH is greater than 5, fermentation did not occur.

For more information on ensiling corn, check out NDSU publication AS-1254, "Silage Fermentation and Preservation." It's available online at www.ag.ndsu.edu/pubs/ansci/dairy/as1254w.htm.

Source: NDSU Extension Communications