Methods to Preserve High Moisture Corn During Storage and Feed-out Mike
Rankin
High moisture corn offers some unique preservation challenges
compared to corn silage because it ferments more slowly and less extensively
while containing high levels of starch, which promotes aerobic
deterioration. Any aid to
hasten fermentation, use up available oxygen, and inhibit yeast growth (once
exposed to oxygen) is beneficial in the ensiling process.
Several options are currently available to producers.
Here's a quick rundown of each. Standard inoculants
High moisture corn inoculants have been available for many years.
These can increase the speed of fermentation and reduce dry matter
loss. They MAY also increase
animal performance. Choose an
inoculant that has been specifically developed for ensiling high
moisture corn. Specific strains
of bacteria may not grow well on all crops and across a wide range of
moisture contents. Thus, a corn
silage inoculant may or may not work well under the drier conditions of high
moisture corn. Most standard
high moisture corn inoculants were developed to improve fermentation.
For this reason, aerobic stability during and after feed-out may not
be significantly improved. In fact, some standard lactic acid producing bacterial
inoculants may actually improve fermentation (good) but decrease aerobic
stability (bad). New strains of bacteria are becoming available that will
improve both fermentation and aerobic stability.
With all inoculants, it is important to follow the manufacturer’s
application rates. Typical rates are between 100,000 and 500,000 colony
forming units (cfu) per gram of high moisture corn. Lactobacillus buchneri
Lactobacillus buchneri
is a unique bacterial inoculant that has been developed to improve aerobic
stability of silages by reducing the growth of yeasts.
The net result is that silages and grains inoculated with L.
buchneri are more resistant to heating at feed-out (exposed to air) as
compared to untreated silages.
L. buchneri
was originally isolated from naturally occurring aerobically stable silages.
It is a heterofermentative bacteria that produces both lactic and
acetic acid during fermentation. Most
bacterial silage inoculants produce primarily lactic acid during the
fermentation process. Silages
treated with an effective dose (600,000 CFU/gram of wet corn) of L.
buchneri have higher concentrations of acetic acid and lower levels of
lactic acid than untreated silages.
The beneficial impact of L. buchneri appears to be related to
the production of acetic acid. Although
the precise mechanism has not yet been determined it is likely that aerobic
stability is improved because acetic acid inhibits growth of specific
species of yeast that are responsible for heating upon exposure to oxygen.
In research trials yeast and mold growth in silage or corn treated with L.
buchneri has been lower at feed-out than for untreated control feeds.
Yeast and mold levels in high moisture corn inoculated with L.
buchneri also do not increase as rapidly as in untreated controls when
exposed to air. As a result,
the temperature of fermented feed inoculated with L. buchneri does
not readily rise upon exposure to air and tends to remain similar to ambient
temperature for several days, even in warm weather.
Using L. buchneri often results in a slightly higher dry
matter loss during fermentation compared to standard homofermentative
bacterial inoculants. It is
unlikely that L. buchneri will improve silage quality in situations
where silage has a history of being aerobically stable at feed out.
In fact, under such circumstances, the potential reduction in silage
dry matter recovery due to this organism’s heterofermentative fermentation
may actually make L. buchneri a less desirable silage inoculant than
homofermentative bacterial inoculants. Propionic acid
Preserving high moisture corn with propionic acid has been a proven
effective practice for many years. However,
it is more costly than simply using an inoculant and requires specialized
equipment to apply. There are
several situations where the use of propionic acid to reduce pH and preserve
corn makes good sense. In years
past, some producers have successfully used concrete or wood floors/bins to
store high moisture corn. In this case, it’s a must that corn be treated
with propionic acid. Applying
propionic acid at the proper rate reduces the pH of preserved corn to about
4.0 and inhibits the growth of harmful microorganisms. The cost of treatment
is usually comparable to that of on-farm drying.
The proper application rate depends upon two factors: 1) the moisture
content of the grain, and 2) the intended length of storage.
Rates are determined based upon pounds of actual acid.
It is most economical to treat corn with acid when kernel moisture is
around 30 percent. It typically takes 10 to 20 lbs. of actual acid to fully
preserve high moisture corn. A
bulletin outlining procedures and rates of propionic acid is available from
our office (929-3171). Another situation where acid may prove beneficial is when an upright silo is being filled but not fed from for an extended period of time. In this case, producers often only apply acid to corn that will fill the last 5 to 10 feet at the top of the silo. It is at the top where spoilage is most likely to occur as a result of oxygen infiltrating the grain. Again, the rate should be determined based on length of storage and moisture.
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